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Kamuda K, Ronzoni R, Majumdar A, Guan FHX, Irving JA, Lomas DA. A novel pathological mutant reveals the role of torsional flexibility in the serpin breach in adoption of an aggregation-prone intermediate. FEBS J 2024; 291:2937-2954. [PMID: 38523412 DOI: 10.1111/febs.17121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 02/17/2024] [Accepted: 03/07/2024] [Indexed: 03/26/2024]
Abstract
Mutants of alpha-1-antitrypsin cause the protein to self-associate and form ordered aggregates ('polymers') that are retained within hepatocytes, resulting in a predisposition to the development of liver disease. The associated reduction in secretion, and for some mutants, impairment of function, leads to a failure to protect lung tissue against proteases released during the inflammatory response and an increased risk of emphysema. We report here a novel deficiency mutation (Gly192Cys), that we name the Sydney variant, identified in a patient in heterozygosity with the Z allele (Glu342Lys). Cellular analysis revealed that the novel variant was mostly retained as insoluble polymers within the endoplasmic reticulum. The basis for this behaviour was investigated using biophysical and structural techniques. The variant showed a 40% reduction in inhibitory activity and a reduced stability as assessed by thermal unfolding experiments. Polymerisation involves adoption of an aggregation-prone intermediate and paradoxically the energy barrier for transition to this state was increased by 16% for the Gly192Cys variant with respect to the wild-type protein. However, with activation to the intermediate state, polymerisation occurred at a 3.8-fold faster rate overall. X-ray crystallography provided two crystal structures of the Gly192Cys variant, revealing perturbation within the 'breach' region with Cys192 in two different orientations: in one structure it faces towards the hydrophobic core while in the second it is solvent-exposed. This orientational heterogeneity was confirmed by PEGylation. These data show the critical role of the torsional freedom imparted by Gly192 in inhibitory activity and stability against polymerisation.
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Affiliation(s)
- Kamila Kamuda
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - Riccardo Ronzoni
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - Avik Majumdar
- AW Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Sydney, Australia
- Victorian Liver Transplant Unit, Austin Health, Melbourne, Australia
- The University of Melbourne, Melbourne, Australia
| | - Fiona H X Guan
- AW Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Sydney, Australia
| | - James A Irving
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
| | - David A Lomas
- Division of Medicine, UCL Respiratory, Rayne Institute, University College London, UK
- Institute of Structural and Molecular Biology, Birkbeck College, University College London, UK
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2
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Ryø LB, Haslund D, Rovsing AB, Pihl R, Sanrattana W, de Maat S, Palarasah Y, Maas C, Thiel S, Mikkelsen JG. Restriction of C1-inhibitor activity in hereditary angioedema by dominant-negative effects of disease-associated SERPING1 gene variants. J Allergy Clin Immunol 2023; 152:1218-1236.e9. [PMID: 37301409 DOI: 10.1016/j.jaci.2023.04.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/17/2023] [Accepted: 04/25/2023] [Indexed: 06/12/2023]
Abstract
BACKGROUND Patients with hereditary angioedema experience recurrent, sometimes life-threatening, attacks of edema. It is a rare genetic disorder characterized by genetic and clinical heterogenicity. Most cases are caused by genetic variants in the SERPING1 gene leading to plasma deficiency of the encoded protein C1 inhibitor (C1INH). More than 500 different hereditary angioedema-causing variants have been identified in the SERPING1 gene, but the disease mechanisms by which they result in pathologically low C1INH plasma levels remain largely unknown. OBJECTIVES The aim was to describe trans-inhibitory effects of full-length or near full-length C1INH encoded by 28 disease-associated SERPING1 variants. METHODS HeLa cells were transfected with expression constructs encoding the studied SERPING1 variants. Extensive and comparative studies of C1INH expression, secretion, functionality, and intracellular localization were carried out. RESULTS Our findings characterized functional properties of a subset of SERPING1 variants allowing the examined variants to be subdivided into 5 different clusters, each containing variants sharing specific molecular characteristics. For all variants except 2, we found that coexpression of mutant and normal C1INH negatively affected the overall capacity to target proteases. Strikingly, for a subset of variants, intracellular formation of C1INH foci was detectable only in heterozygous configurations enabling simultaneous expression of normal and mutant C1INH. CONCLUSIONS We provide a functional classification of SERPING1 gene variants suggesting that different SERPING1 variants drive the pathogenicity through different and in some cases overlapping molecular disease mechanisms. For a subset of gene variants, our data define some types of hereditary angioedema with C1INH deficiency as serpinopathies driven by dominant-negative disease mechanisms.
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Affiliation(s)
| | - Didde Haslund
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Rasmus Pihl
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Wariya Sanrattana
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Steven de Maat
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Yaseelan Palarasah
- Department of Cancer and Inflammation Research, University of Southern Denmark, Odense, Denmark; Department of Clinical Biochemistry, Hospital of South West Jutland, Esbjerg, Denmark
| | - Coen Maas
- CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands; Unit for Thrombosis Research, Department of Regional Health Research, University of Southern Denmark, Esbjerg, Denmark
| | - Steffen Thiel
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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Long-range allostery mediates the regulation of plasminogen activator inhibitor-1 by cell adhesion factor vitronectin. J Biol Chem 2022; 298:102652. [PMID: 36444882 PMCID: PMC9731859 DOI: 10.1016/j.jbc.2022.102652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 10/24/2022] [Accepted: 10/26/2022] [Indexed: 11/05/2022] Open
Abstract
The serpin plasminogen activator inhibitor 1 (PAI-1) spontaneously undergoes a massive structural change from a metastable and active conformation, with a solvent-accessible reactive center loop (RCL), to a stable, inactive, or latent conformation, with the RCL inserted into the central β-sheet. Physiologically, conversion to the latent state is regulated by the binding of vitronectin, which hinders the latency transition rate approximately twofold. The molecular mechanisms leading to this rate change are unclear. Here, we investigated the effects of vitronectin on the PAI-1 latency transition using all-atom path sampling simulations in explicit solvent. In simulated latency transitions of free PAI-1, the RCL is quite mobile as is the gate, the region that impedes RCL access to the central β-sheet. This mobility allows the formation of a transient salt bridge that facilitates the transition; this finding rationalizes existing mutagenesis results. Vitronectin binding reduces RCL and gate mobility by allosterically rigidifying structural elements over 40 Å away from the binding site, thus blocking transition to the latent conformation. The effects of vitronectin are propagated by a network of dynamically correlated residues including a number of conserved sites that were previously identified as important for PAI-1 stability. Simulations also revealed a transient pocket populated only in the vitronectin-bound state, corresponding to a cryptic drug-binding site identified by crystallography. Overall, these results shed new light on PAI-1 latency transition regulation by vitronectin and illustrate the potential of path sampling simulations for understanding functional protein conformational changes and for facilitating drug discovery.
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4
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Tolstyko EA, Chergintsev DA, Tolicheva OA, Vinogradova DS, Konevega AL, Morozov SY, Solovyev AG. RNA Binding by Plant Serpins in vitro. BIOCHEMISTRY. BIOKHIMIIA 2021; 86:1214-1224. [PMID: 34903159 DOI: 10.1134/s0006297921100059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Serpins constitute a large family of protease inhibitors with regulatory functions found in all living organisms. Most plant serpins have not been functionally characterized, with the exception of Arabidopsis thaliana AtSerpin1, an inhibitor of pro-apoptotic proteases, which is involved in the regulation of the programmed cell death induction, and Cucurbita maxima CmPS1, a phloem protein, which presumably inhibits insect digestive proteases and binds RNA. CmPS1 interacts most efficiently with highly structured RNA; in particular, it forms a specific complex with tRNA. Here, we demonstrated that AtSerpin1 also forms a complex with tRNA. Analysis of tRNA species bound by AtSerpin1 and CmPS1 in the presence of tRNA excess revealed that both proteins have no strict selectivity for individual tRNAs, suggesting specific interaction of AtSerpin1 and CmPS1 proteins with elements of the secondary/tertiary structure universal for all tRNAs. Analysis of CmPS1 binding of the microRNA precursor pre-miR390 and its mutants demonstrated that the pre-miR390 mutant with a perfect duplex in the hairpin stem lost the ability to form a discrete complex with CmPS1, whereas another variant of pre-miR390 with the native unpaired nucleotide residues in the stem retained this ability. These data indicate that specific interactions of plant serpins with structured RNA are based on the recognition of structurally unique spatial motifs formed with the participation of unpaired nucleotide residues in the RNA duplexes.
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Affiliation(s)
- Eugene A Tolstyko
- Department of Virology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia.,Konstantinov St.-Petersburg Nuclear Physics Institute of National Research Center "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia
| | - Denis A Chergintsev
- Department of Plant Physiology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Olga A Tolicheva
- Konstantinov St.-Petersburg Nuclear Physics Institute of National Research Center "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia
| | - Dariya S Vinogradova
- Konstantinov St.-Petersburg Nuclear Physics Institute of National Research Center "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia.,NanoTemper Technologies Rus, Saint Petersburg, 191167, Russia
| | - Andrey L Konevega
- Konstantinov St.-Petersburg Nuclear Physics Institute of National Research Center "Kurchatov Institute", Gatchina, Leningrad Region, 188300, Russia.,Peter the Great Saint Petersburg Polytechnic University, Saint Petersburg, 195251, Russia.,National Research Center "Kurchatov Institute", Moscow, 123182, Russia
| | - Sergey Y Morozov
- Department of Virology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
| | - Andrey G Solovyev
- Department of Virology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia. .,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia
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5
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Laffranchi M, Elliston EL, Miranda E, Perez J, Ronzoni R, Jagger AM, Heyer-Chauhan N, Brantly ML, Fra A, Lomas DA, Irving JA. Intrahepatic heteropolymerization of M and Z alpha-1-antitrypsin. JCI Insight 2020; 5:135459. [PMID: 32699193 PMCID: PMC7453904 DOI: 10.1172/jci.insight.135459] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 06/17/2020] [Indexed: 12/21/2022] Open
Abstract
The α-1-antitrypsin (or alpha-1-antitrypsin, A1AT) Z variant is the primary cause of severe A1AT deficiency and forms polymeric chains that aggregate in the endoplasmic reticulum of hepatocytes. Around 2%-5% of Europeans are heterozygous for the Z and WT M allele, and there is evidence of increased risk of liver disease when compared with MM A1AT individuals. We have shown that Z and M A1AT can copolymerize in cell models, but there has been no direct observation of heteropolymer formation in vivo. To this end, we developed a monoclonal antibody (mAb2H2) that specifically binds to M in preference to Z A1AT, localized its epitope using crystallography to a region perturbed by the Z (Glu342Lys) substitution, and used Fab fragments to label polymers isolated from an MZ heterozygote liver explant. Glu342 is critical to the affinity of mAb2H2, since it also recognized the mild S-deficiency variant (Glu264Val) present in circulating polymers from SZ heterozygotes. Negative-stain electron microscopy of the Fab2H2-labeled liver polymers revealed that M comprises around 6% of the polymer subunits in the MZ liver sample. These data demonstrate that Z A1AT can form heteropolymers with polymerization-inert variants in vivo with implications for liver disease in heterozygous individuals.
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Affiliation(s)
- Mattia Laffranchi
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.,UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Emma Lk Elliston
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Elena Miranda
- Department of Biology and Biotechnologies 'Charles Darwin' and Pasteur Institute - Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy
| | - Juan Perez
- Departamento de Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Campus de Teatinos, Universidad de Malaga, Malaga, Spain
| | - Riccardo Ronzoni
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Alistair M Jagger
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Nina Heyer-Chauhan
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Mark L Brantly
- Division of Pulmonary, Critical Care, and Sleep Medicine, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Annamaria Fra
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - David A Lomas
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - James A Irving
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, United Kingdom
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6
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Zhou J, Zhao H, Zhang L, Ye X, Wang Z, Li Q, Ke H, Zhao G, Du J, Yang S, Zhao L. Effects of bacterial haemorrhagic septicemia on the immune response of Leiocassis longirostris by RNA-Seq and microRNA-Seq. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2020; 34:100659. [PMID: 32070936 DOI: 10.1016/j.cbd.2020.100659] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/29/2020] [Accepted: 01/30/2020] [Indexed: 11/17/2022]
Abstract
Leiocassis longirostris is a common fish variety that is widely cultivated in China, during the breeding process however, it is highly susceptible to bacterial haemorrhagic septicemia, which can cause great economic loss for farmers. To understand the immune responses of L. longirostris to Aeromonas hydrophila infection, Illumina sequencing was employed to identify changes in the mRNA and miRNA in spleen tissue. In this study, a total of 92.16 and 95.61 million (M) high-quality transcriptome reads were generated from the control group (CG) and experimental group (EG) spleen samples, respectively, and 207 up-regulated and 185 down-regulated genes were identified. These genes were enriched in 29 GO terms and 30 KEGG pathways (P ≤ 0.05), including cytokine-cytokine receptor interaction and complement and coagulation cascades, with 17 up-regulated genes and 12 down-regulated genes related to immune responses in the EG relative to the CG. Based on the zebrafish genome, miRNA-seq identified a total of 343 miRNAs, of which 15 were up-regulated and 10 were down-regulated (fold-change ≥2 or ≤0.5 and P ≤ 0.05). Target gene prediction and KEGG enrichment analysis revealed that all of the target genes were concentrated in 13 pathways associated with immune response, including the mTOR signaling pathway and the TGF-beta signaling pathway. The expression patterns of 8 differentially expressed genes and 4 miRNAs involved in immune response were validated by quantitative real-time RT-PCR. These results have provided valuable insights into the molecular mechanisms underlying the immune response of L. longirostris to bacterial haemorrhagic septicemia.
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Affiliation(s)
- Jian Zhou
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Han Zhao
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Lu Zhang
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Xianlin Ye
- Sichuan Academy of Agricultural Sciences, Chengdu 610066, Sichuan, China
| | - Zhipeng Wang
- Sichuan Academy of Agricultural Sciences, Chengdu 610066, Sichuan, China
| | - Qiang Li
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Hongyu Ke
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Gang Zhao
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Jun Du
- Fisheries Institute, Sichuan Academy of Agricultural Sciences, Chengdu 611731, Sichuan, China
| | - Song Yang
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Liulan Zhao
- College of Animal Science and Technology, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
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Abstract
Serine proteinase inhibitors (serpins), typically fold to a metastable native state and undergo a major conformational change in order to inhibit target proteases. However, conformational lability of the native serpin fold renders them susceptible to misfolding and aggregation, and underlies misfolding diseases such as α1-antitrypsin deficiency. Serpin specificity towards its protease target is dictated by its flexible and solvent exposed reactive centre loop (RCL), which forms the initial interaction with the target protease during inhibition. Previous studies have attempted to alter the specificity by mutating the RCL to that of a target serpin, but the rules governing specificity are not understood well enough yet to enable specificity to be engineered at will. In this paper, we use conserpin, a synthetic, thermostable serpin, as a model protein with which to investigate the determinants of serpin specificity by engineering its RCL. Replacing the RCL sequence with that from α1-antitrypsin fails to restore specificity against trypsin or human neutrophil elastase. Structural determination of the RCL-engineered conserpin and molecular dynamics simulations indicate that, although the RCL sequence may partially dictate specificity, local electrostatics and RCL dynamics may dictate the rate of insertion during protease inhibition, and thus whether it behaves as an inhibitor or a substrate. Engineering serpin specificity is therefore substantially more complex than solely manipulating the RCL sequence, and will require a more thorough understanding of how conformational dynamics achieves the delicate balance between stability, folding and function required by the exquisite serpin mechanism of action.
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8
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Li M, Christen JM, Dittmer NT, Cao X, Zhang X, Jiang H, Kanost MR. The Manduca sexta serpinome: Analysis of serpin genes and proteins in the tobacco hornworm. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 102:21-30. [PMID: 30237077 PMCID: PMC6249112 DOI: 10.1016/j.ibmb.2018.09.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/14/2018] [Accepted: 09/16/2018] [Indexed: 06/02/2023]
Abstract
Members of the serpin superfamily of proteins occur in animals, plants, bacteria, archaea and some viruses. They adopt a variety of physiological functions, including regulation of immune system, modulation of apoptosis, hormone transport and acting as storage proteins. Most members of the serpin family are inhibitors of serine proteinases. In this study, we searched the genome of Manduca sexta and identified 32 serpin genes. We analyzed the structure of these genes and the sequences of their encoded proteins. Three M. sexta genes (serpin-1, serpin-15, and serpin-28) have mutually exclusive alternatively spliced exons encoding the carboxyl-terminal reactive center loop of the protein, which is the site of interaction with target proteases. We discovered that MsSerpin-1 has 14 splicing isoforms, including two undiscovered in previous studies. Twenty-eight of the 32 M. sexta serpins include a putative secretion signal peptide and are predicted to be extracellular proteins. Phylogenetic analysis of serpins in M. sexta and Bombyx mori indicates that 17 are orthologous pairs, perhaps carrying out essential physiological functions. Analysis of the reactive center loop and hinge regions of the protein sequences indicates that 16 of the serpin genes encode proteins that may lack proteinase inhibitor activity. Our annotation and analysis of these serpin genes and their transcript profiles should lead to future advances in experimental study of their functions in insect biochemistry.
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Affiliation(s)
- Miao Li
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Jayne M Christen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Neal T Dittmer
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Xiaolong Cao
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Xiufeng Zhang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Haobo Jiang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Michael R Kanost
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.
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Lin H, Lin X, Zhu J, Yu XQ, Xia X, Yao F, Yang G, You M. Characterization and expression profiling of serine protease inhibitors in the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae). BMC Genomics 2017; 18:162. [PMID: 28196471 PMCID: PMC5309989 DOI: 10.1186/s12864-017-3583-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 02/10/2017] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Serine protease inhibitors (SPIs) have been found in all living organisms and play significant roles in digestion, development and innate immunity. In this study, we present a genome-wide identification and expression profiling of SPI genes in the diamondback moth, Plutella xylostella (L.), a major pest of cruciferous crops with global distribution and broad resistance to different types of insecticides. RESULTS A total of 61 potential SPI genes were identified in the P. xylostella genome, and these SPIs were classified into serpins, canonical inhibitors, and alpha-2-macroglobulins based on their modes of action. Sequence alignments showed that amino acid residues in the hinge region of known inhibitory serpins from other insect species were conserved in most P. xylostella serpins, suggesting that these P. xylostella serpins may be functionally active. Phylogenetic analysis confirmed that P. xylostella inhibitory serpins were clustered with known inhibitory serpins from six other insect species. More interestingly, nine serpins were highly similar to the orthologues in Manduca sexta which have been demonstrated to participate in regulating the prophenoloxidase activation cascade, an important innate immune response in insects. Of the 61 P.xylostella SPI genes, 33 were canonical SPIs containing seven types of inhibitor domains, including Kunitz, Kazal, TIL, amfpi, Antistasin, WAP and Pacifastin. Moreover, some SPIs contained additional non-inhibitor domains, including spondin_N, reeler, and other modules, which may be involved in protein-protein interactions. Gene expression profiling showed gene-differential, stage- and sex-specific expression patterns of SPIs, suggesting that SPIs may be involved in multiple physiological processes in P. xylostella. CONCLUSIONS This is the most comprehensive investigation so far on SPI genes in P. xylostella. The characterized features and expression patterns of P. xylostella SPIs indicate that the SPI family genes may be involved in innate immunity of this species. Our findings provide valuable information for uncovering further biological roles of SPI genes in P. xylostella.
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Affiliation(s)
- Hailan Lin
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China
| | - Xijian Lin
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China
| | - Jiwei Zhu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China
| | - Xiao-Qiang Yu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,School of Biological Sciences, University of Missouri, Kansas City, MO, 64110-2499, USA
| | - Xiaofeng Xia
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China
| | - Fengluan Yao
- Institute of Plant Protection, Fujian Academy of Agricultural Sciences, Fuzhou, 350013, China
| | - Guang Yang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China
| | - Minsheng You
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, and College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. .,Institute of Applied Ecology and Research Centre for Biodiversity and Eco-Safety, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. .,Fujian-Taiwan Joint Innovation Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, 350002, China. .,Key Laboratory of Integrated Pest Management of Fujian and Taiwan, China Ministry of Agriculture, Fuzhou, 350002, China.
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10
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Motamedi-Shad N, Jagger AM, Liedtke M, Faull SV, Nanda AS, Salvadori E, Wort JL, Kay CW, Heyer-Chauhan N, Miranda E, Perez J, Ordóñez A, Haq I, Irving JA, Lomas DA. An antibody that prevents serpin polymerisation acts by inducing a novel allosteric behaviour. Biochem J 2016; 473:3269-90. [PMID: 27407165 PMCID: PMC5264506 DOI: 10.1042/bcj20160159] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 07/08/2016] [Accepted: 07/12/2016] [Indexed: 11/30/2022]
Abstract
Serpins are important regulators of proteolytic pathways with an antiprotease activity that involves a conformational transition from a metastable to a hyperstable state. Certain mutations permit the transition to occur in the absence of a protease; when associated with an intermolecular interaction, this yields linear polymers of hyperstable serpin molecules, which accumulate at the site of synthesis. This is the basis of many pathologies termed the serpinopathies. We have previously identified a monoclonal antibody (mAb4B12) that, in single-chain form, blocks α1-antitrypsin (α1-AT) polymerisation in cells. Here, we describe the structural basis for this activity. The mAb4B12 epitope was found to encompass residues Glu32, Glu39 and His43 on helix A and Leu306 on helix I. This is not a region typically associated with the serpin mechanism of conformational change, and correspondingly the epitope was present in all tested structural forms of the protein. Antibody binding rendered β-sheet A - on the opposite face of the molecule - more liable to adopt an 'open' state, mediated by changes distal to the breach region and proximal to helix F. The allosteric propagation of induced changes through the molecule was evidenced by an increased rate of peptide incorporation and destabilisation of a preformed serpin-enzyme complex following mAb4B12 binding. These data suggest that prematurely shifting the β-sheet A equilibrium towards the 'open' state out of sequence with other changes suppresses polymer formation. This work identifies a region potentially exploitable for a rational design of ligands that is able to dynamically influence α1-AT polymerisation.
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Affiliation(s)
- Neda Motamedi-Shad
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - Alistair M. Jagger
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - Maximilian Liedtke
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
| | - Sarah V. Faull
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, U.K
| | - Arjun Scott Nanda
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - Enrico Salvadori
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, U.K
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, U.K
| | - Joshua L. Wort
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - Christopher W.M. Kay
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
- London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, U.K
| | - Narinder Heyer-Chauhan
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - Elena Miranda
- Department of Biology and Biotechnologies ‘Charles Darwin’, Sapienza University of Rome, Rome 00185, Italy
| | - Juan Perez
- Departamento de Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Campus Teatinos, Universidad de Malaga, Malaga 29071, Spain
| | - Adriana Ordóñez
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, U.K
| | - Imran Haq
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - James A. Irving
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
| | - David A. Lomas
- Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K
- Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K
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11
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Abstract
Although proteins generally fold to their thermodynamically most stable state, some metastable proteins populate higher free energy states. Conformational changes from metastable higher free energy states to lower free energy states with greater stability can then generate the work required to perform physiologically important functions. However, how metastable proteins fold to these higher free energy states in the cell and avoid more stable but inactive conformations is poorly understood. The serpin family of metastable protease inhibitors uses large conformational changes that are downhill in free energy to inhibit target proteases by pulling apart the protease active site. The serpin antithrombin III (ATIII) targets thrombin and other proteases involved in blood coagulation, and ATIII misfolding can thus lead to thrombosis and other diseases. ATIII has three disulfide bonds, two near the N terminus and one near the C terminus. Our studies of ATIII in-cell folding reveal a surprising, biased order of disulfide bond formation, with early formation of the C-terminal disulfide, before formation of the N-terminal disulfides, critical for folding to the active, metastable state. Early folding of the predominantly β-sheet ATIII domain in this two-domain protein constrains the reactive center loop (RCL), which contains the protease-binding site, ensuring that the RCL remains accessible. N-linked glycans and carbohydrate-binding molecular chaperones contribute to the efficient folding and secretion of functional ATIII. The inability of a number of disease-associated ATIII variants to navigate the folding reaction helps to explain their disease phenotypes.
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12
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Deller MC, Kong L, Rupp B. Protein stability: a crystallographer's perspective. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2016; 72:72-95. [PMID: 26841758 PMCID: PMC4741188 DOI: 10.1107/s2053230x15024619] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 12/21/2015] [Indexed: 12/18/2022]
Abstract
Protein stability is a topic of major interest for the biotechnology, pharmaceutical and food industries, in addition to being a daily consideration for academic researchers studying proteins. An understanding of protein stability is essential for optimizing the expression, purification, formulation, storage and structural studies of proteins. In this review, discussion will focus on factors affecting protein stability, on a somewhat practical level, particularly from the view of a protein crystallographer. The differences between protein conformational stability and protein compositional stability will be discussed, along with a brief introduction to key methods useful for analyzing protein stability. Finally, tactics for addressing protein-stability issues during protein expression, purification and crystallization will be discussed.
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Affiliation(s)
- Marc C Deller
- Stanford ChEM-H, Macromolecular Structure Knowledge Center, Stanford University, Shriram Center, 443 Via Ortega, Room 097, MC5082, Stanford, CA 94305-4125, USA
| | - Leopold Kong
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Building 8, Room 1A03, 8 Center Drive, Bethesda, MD 20814, USA
| | - Bernhard Rupp
- Department of Forensic Crystallography, k.-k. Hofkristallamt, 91 Audrey Place, Vista, CA 92084, USA
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13
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Vibrational spectroscopic analysis of peripheral blood plasma of patients with Alzheimer’s disease. Anal Bioanal Chem 2015; 407:7747-56. [DOI: 10.1007/s00216-015-8940-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/17/2015] [Accepted: 07/24/2015] [Indexed: 12/25/2022]
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14
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A new model for pore formation by cholesterol-dependent cytolysins. PLoS Comput Biol 2014; 10:e1003791. [PMID: 25144725 PMCID: PMC4140638 DOI: 10.1371/journal.pcbi.1003791] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 07/01/2014] [Indexed: 11/19/2022] Open
Abstract
Cholesterol Dependent Cytolysins (CDCs) are important bacterial virulence factors that form large (200–300 Å) membrane embedded pores in target cells. Currently, insights from X-ray crystallography, biophysical and single particle cryo-Electron Microscopy (cryo-EM) experiments suggest that soluble monomers first interact with the membrane surface via a C-terminal Immunoglobulin-like domain (Ig; Domain 4). Membrane bound oligomers then assemble into a prepore oligomeric form, following which the prepore assembly collapses towards the membrane surface, with concomitant release and insertion of the membrane spanning subunits. During this rearrangement it is proposed that Domain 2, a region comprising three β-strands that links the pore forming region (Domains 1 and 3) and the Ig domain, must undergo a significant yet currently undetermined, conformational change. Here we address this problem through a systematic molecular modeling and structural bioinformatics approach. Our work shows that simple rigid body rotations may account for the observed collapse of the prepore towards the membrane surface. Support for this idea comes from analysis of published cryo-EM maps of the pneumolysin pore, available crystal structures and molecular dynamics simulations. The latter data in particular reveal that Domains 1, 2 and 4 are able to undergo significant rotational movements with respect to each other. Together, our data provide new and testable insights into the mechanism of pore formation by CDCs. Pore formation is central to the ability of cholesterol dependent cytolysins (CDCs) to act as important bacterial virulence factors. Secreted by numerous pathogens the toxins assemble into a circular ring and then perforate the target membrane to form the largest self-assembling proteinaceous pores known. In this paper we investigated computationally the conformational properties of the CDC molecule and deduced a new structural model of pore formation and membrane insertion that reconciles all experimental data. The mechanism of membrane perforation by CDCs put forward here reveals concerted and unsuspected domains motion of large amplitude, which conflicts with the currently proposed model. The work presented here procures a plausible structural mechanism of CDC oligomeric transition and furthers our understanding of pore formation by these important toxins.
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15
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Functional analysis of novel alpha-1 antitrypsin variants G320R and V321F. Mol Biol Rep 2014; 41:6133-41. [PMID: 24969485 DOI: 10.1007/s11033-014-3492-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 06/17/2014] [Indexed: 12/12/2022]
Abstract
Alpha-1 antitrypsin (AAT) gene is highly polymorphic, with a large number of rare variants whose phenotypic consequences often remain inconclusive. Studies addressing functional characteristics of AAT variants are of significant biomedical importance since deficiency and dysfunctionality of AAT are associated with liver and lung diseases. We report the results of the functional analysis of two naturally occurring AAT variants, G320R and V321F, previously identified in patients with lung disease. Neither of variants has been fully functionally characterized. In order to perform their functional analysis both variants were expressed in prokaryotic and eukaryotic systems and their intracellular localization, activity, stability, and polymerization were determined. The results of this study demonstrated that variants G320R and V321F have neither impaired activity against porcine pancreatic elastase nor propensity to form polymers. However, both variants had altered electrophoretic mobility and reduced thermostability when compared to M variant of the protein, indicating a slightly impaired secondary or tertiary structure.
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16
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McCarthy C, Saldova R, Wormald MR, Rudd PM, McElvaney NG, Reeves EP. The Role and Importance of Glycosylation of Acute Phase Proteins with Focus on Alpha-1 Antitrypsin in Acute and Chronic Inflammatory Conditions. J Proteome Res 2014; 13:3131-43. [DOI: 10.1021/pr500146y] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Cormac McCarthy
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
| | - Radka Saldova
- NIBRT
GlycoScience Group, The National Institute for Bioprocessing Research
and Training, University College Dublin, Dublin 4, Ireland
| | - Mark R Wormald
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, Oxford OX1 3QU, U.K
| | - Pauline M. Rudd
- NIBRT
GlycoScience Group, The National Institute for Bioprocessing Research
and Training, University College Dublin, Dublin 4, Ireland
| | - Noel G. McElvaney
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
| | - Emer P. Reeves
- Respiratory
Research Division, Royal College of Surgeons in Ireland, Beaumont
Hospital, Dublin 9, Ireland
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17
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The roles of helix I and strand 5A in the folding, function and misfolding of α1-antitrypsin. PLoS One 2013; 8:e54766. [PMID: 23382962 PMCID: PMC3558512 DOI: 10.1371/journal.pone.0054766] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 12/14/2012] [Indexed: 11/19/2022] Open
Abstract
α1-Antitrypsin, the archetypal member of the serpin superfamily, is a metastable protein prone to polymerization when exposed to stressors such as elevated temperature, low denaturant concentrations or through the presence of deleterious mutations which, in a physiological context, are often associated with disease. Experimental evidence suggests that α1-Antitrypsin can polymerize via several alternative mechanisms in vitro. In these polymerization mechanisms different parts of the molecule are proposed to undergo conformational change. Both strand 5 and helix I are proposed to adopt different conformations when forming the various polymers, and possess a number of highly conserved residues however their role in the folding and misfolding of α1-Antitrypsin has never been examined. We have therefore created a range of α1Antitypsin variants in order to explore the role of these conserved residues in serpin folding, misfolding, stability and function. Our data suggest that key residues in helix I mediate efficient folding from the folding intermediate and residues in strand 5A ensure native state stability in order to prevent misfolding. Additionally, our data indicate that helix I is involved in the inhibitory process and that both structural elements undergo differing conformational rearrangements during unfolding and misfolding. These findings suggest that the ability of α1-Antitrypsin to adopt different types of polymers under different denaturing conditions may be due to subtle conformational differences in the transiently populated structures adopted prior to the I and M* states.
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18
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Structural basis for catalytic activation of protein Z-dependent protease inhibitor (ZPI) by protein Z. Blood 2012; 120:1726-33. [PMID: 22786881 DOI: 10.1182/blood-2012-03-419598] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The anticoagulant serpin, protein Z-dependent protease inhibitor (ZPI), is catalytically activated by its cofactor, protein Z (PZ), to regulate the function of blood coagulation factor Xa on membrane surfaces. The X-ray structure of the ZPI-PZ complex has shown that PZ binds to a unique site on ZPI centered on helix G. In the present study, we show by Ala-scanning mutagenesis of the ZPI-binding interface, together with native PAGE and kinetic analyses of PZ binding to ZPI, that Tyr240 and Asp293 of ZPI are crucial hot spots for PZ binding. Complementary studies with protein Z-protein C chimeras show the importance of both pseudocatalytic and EGF2 domains of PZ for the critical ZPI interactions. To understand how PZ acts catalytically, we analyzed the interaction of reactive loop-cleaved ZPI (cZPI) with PZ and determined the cZPI X-ray structure. The cZPI structure revealed changes in helices A and G of the PZ-binding site relative to native ZPI that rationalized an observed 6-fold loss in PZ affinity and PZ catalytic action. These findings identify the key determinants of catalytic activation of ZPI by PZ and suggest novel strategies for ameliorating hemophilic states through drugs that disrupt the ZPI-PZ interaction.
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19
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Abstract
Essentially the same steps are required to solve the crystal structure of a serpin as for any other protein: produce and purify protein, grow crystals, collect diffraction data, find estimates of the phase angles, and then refine and validate the structure. For the phasing step, experimental phasing methods involving heavy atom soaks were required for the first few structures, but with the large number of serpin structures now available, molecular replacement has become the method of choice. Two things are special about serpins. First, because of the central role of conformational change in serpin mechanism, it is advisable to consider a variety of molecular replacement models in different conformations and then to allow for rigid-body motions in the initial refinement steps. Second, probably owing to the flexibility of serpins, the average serpin crystal is significantly less well ordered than the average crystal of another protein, which increases the difficulty of solving and refining their structures.
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20
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Knaupp AS, Bottomley SP. Structural change in β-sheet A of Z α(1)-antitrypsin is responsible for accelerated polymerization and disease. J Mol Biol 2011; 413:888-98. [PMID: 21945526 DOI: 10.1016/j.jmb.2011.09.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 09/07/2011] [Accepted: 09/11/2011] [Indexed: 11/26/2022]
Abstract
The presence of the Z mutation (Glu342Lys) is responsible for more than 95% of α(1)-antitrypsin (α(1)AT) deficiency cases. It leads to increased polymerization of the serpin α(1)AT during its synthesis and in circulation. It has been proposed that the Z mutation results in a conformational change within the folded state of antitrypsin that enhances its polymerization. In order to localize the conformational change, we have created two single tryptophan mutants of Z α(1)AT and analyzed their fluorescence properties. α(1)AT contains two tryptophan residues that are located in distinct regions of the molecule: Trp194 at the top of β-sheet A and Trp238 on β-sheet B. We have replaced each tryptophan residue individually with a phenylalanine in order to study the local environment of the remaining tryptophan residue in both M and Z α(1)AT. A detailed fluorescence spectroscopic analysis of each mutant was carried out, and we detected differences in the emission spectrum, the Stern-Volmer constant for potassium iodide quenching and the anisotropy of only Trp194 in Z α(1)AT compared to M α(1)AT. Our data reveal that the Z mutation results in a conformational change at the top of β-sheet A but does not affect the structural integrity of β-sheet B.
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Affiliation(s)
- Anja S Knaupp
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia
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21
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22
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Abstract
Plasminogen activator inhibitor-1 (PAI-1) belongs to the serine protease inhibitor super family (serpin) and is the primary inhibitor of both the tissue-type (tPA) and urokinase-type (uPA) plasminogen activators. PAI-1 has been implicated in a wide range of pathological processes where it may play a direct role in a variety of diseases. These observations have made PAI-1 an attractive target for small molecule drug development. However, PAI-1's structural plasticity and its capacity to interact with multiple ligands have made the identification and development of such small molecule PAI-1 inactivating agents challenging. In the following pages, we discuss the difficulties associated with screening for small molecule inactivators of PAI-1, in particular, and of serpins, in general. We discuss strategies for high-throughput screening (HTS) of chemical and natural product libraries, and validation steps necessary to confirm identified hits. Finally, we describe steps essential to confirm specificity of active compounds, and strategies to examine potential mechanisms of compound action.
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23
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Ljujic M, Topic A, Nikolic A, Divac A, Grujic M, Mitic-Milikic M, Radojkovic D. Identification of a rare p.G320R alpha-1-antitrypsin variant in emphysema and lung cancer patients. Genet Mol Biol 2010; 33:5-8. [PMID: 21637596 PMCID: PMC3036068 DOI: 10.1590/s1415-47572009005000100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 07/07/2009] [Indexed: 12/05/2022] Open
Abstract
The alpha-1-antitrypsin (A1AT) gene is highly polymorphic, with more than 100 genetic variants identified of which some can affect A1AT protein concentration and/or function and lead to pulmonary and/or liver disease. This study reports on the characterization of a p.G320R variant found in two patients, one with emphysema and the other with lung cancer. This variant results from a single base-pair substitution in exon 4 of the A1AT gene, and has been characterized as P by isoelectric focusing. Functional evaluation of the A1AT p.G320R variant was through comparing specific trypsin inhibitory activity in two patients with pulmonary disorders, carriers of the p.G320R variant, and 19 healthy individuals, carriers of normal A1AT M variants. Results showed that specific trypsin inhibitory activity was lower in both emphysema (2.45 mU/g) and lung cancer (2.07 mU/g) patients than in carriers of the normal variants (range 2.51-3.71 mU/g). This rare A1AT variant is associated with reduced functional activity of A1AT protein. Considering that it was found in patients with severe pulmonary disorders, this variant could be of clinical significance.
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Affiliation(s)
- Mila Ljujic
- Institute of Molecular Genetics and Genetic Engineering, Belgrade Serbia
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24
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The serpin gene family in Anopheles gambiae. Gene 2009; 442:47-54. [PMID: 19394412 DOI: 10.1016/j.gene.2009.04.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/10/2009] [Accepted: 04/17/2009] [Indexed: 12/16/2022]
Abstract
Serpins (serine protease inhibitors) regulate some innate immune responses of insects by inhibiting endogenous proteases. In this study, we characterized the serpin (SRPN) gene family in the mosquito Anopheles gambiae, the major malaria vector in Sub-Saharan Africa. We identified 18 A. gambiae SRPN genes, all on chromosomes 2 and 3, through searches of genomic DNA and EST databases. In addition to SRPN10, previously documented to exhibit alternative splicing, we found three splicing isoforms of SRPN4. We completed sequencing of cDNAs for the A. gambiae serpins to obtain complete coding sequence information and to verify or improve gene predictions. The predicted SRPN9 and 15 in the initial genome annotation were determined to be a single gene (SRPN9). Sixteen of the serpins contained putative secretion signal sequences. Multiple sequence alignments showing conserved residues important in structural conformation, including the consensus pattern within the hinge region, indicated that most of the A. gambiae serpins may be inhibitory. Phylogenetic analyses confirmed that SRPN1, 2, 3, 8, 9 and 10 formed phylogenetic clusters with known inhibitory serpins from Drosophila melanogaster and Manduca sexta. Many of the A. gambiae serpins were expressed during all life stages. However, SRPN7, 8, 12, and 19 were expressed at very low levels in the adult stage. SRPN13 was expressed mostly in eggs and young larvae, whereas SRPN5 and 14 were expressed mostly in adults. Such differences in expression pattern suggest that the serpins are involved in multiple physiological processes. Determining the biological functions of the mosquito serpins will require future work to identify the proteases they inhibit in vivo.
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25
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Lin HY, Underhill C, Gardill BR, Muller YA, Hammond GL. Residues in the human corticosteroid-binding globulin reactive center loop that influence steroid binding before and after elastase cleavage. J Biol Chem 2008; 284:884-96. [PMID: 19011238 DOI: 10.1074/jbc.m807376200] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Corticosteroid-binding globulin (CBG) is a non-inhibitory serine proteinase inhibitor (serpin) that transports cortisol and progesterone in blood. Crystal structures of rat CBG and a thrombin-cleaved human CBG:anti-trypsin (Pittsburgh) chimera show how structural transitions after proteolytic cleavage of the CBG reactive center loop (RCL) could disrupt steroid binding. This ligand release mechanism is assumed to involve insertion of the cleaved RCL into the beta-sheet A of the serpin structure. We have, therefore, examined how amino acid substitutions in the human CBG RCL influence steroid binding before and after its cleavage by neutrophil elastase. Elastase-cleaved wild-type CBG or variants with substitutions at P15 and/or P16 (E334G/G335N or E334A) lost steroid binding completely, whereas deletion of Glu-334 resulted in no loss of steroid binding after RCL cleavage, presumably because this prevents its insertion into beta-sheet A. Similarly, the steroid binding properties of CBG variants with substitutions at P15 (G335P), P14 (V336R), or P12 (T338P) in the RCL hinge were largely unaffected after elastase cleavage, most likely because the re-orientation and/or insertion of the cleaved RCL was blocked. Substitutions at P10 (G340P, G340S) or P8 (T342P, T342N) resulted in a partial loss of steroid binding after proteolysis which we attribute to incomplete insertion of the cleaved RCL. Remarkably, several substitutions (E334A, V336R, G340S, and T342P) increased the steroid binding affinities of human CBG even before elastase cleavage, consistent with the concept that CBG normally toggles between a high affinity ligand binding state where the RCL is fully exposed and a lower affinity state in which the RCL is partly inserted into beta-sheet A.
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Affiliation(s)
- Hai-Yan Lin
- Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
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26
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Pappalardo E, Caccia S, Suffritti C, Tordai A, Zingale LC, Cicardi M. Mutation screening of C1 inhibitor gene in 108 unrelated families with hereditary angioedema: Functional and structural correlates. Mol Immunol 2008; 45:3536-44. [DOI: 10.1016/j.molimm.2008.05.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Revised: 05/10/2008] [Accepted: 05/14/2008] [Indexed: 11/17/2022]
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27
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Molecular basis of thrombin recognition by protein C inhibitor revealed by the 1.6-A structure of the heparin-bridged complex. Proc Natl Acad Sci U S A 2008; 105:4661-6. [PMID: 18362344 DOI: 10.1073/pnas.0711055105] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Protein C inhibitor (PCI) is a serpin with many roles in biology, including a dual role as pro- and anticoagulant in blood. The protease specificity and local function of PCI depend on its interaction with cofactors such as heparin-like glycosaminoglycans (GAGs) and thrombomodulin (TM). Both cofactors significantly increase the rate of thrombin inhibition, but GAGs serve to promote the anticoagulant activity of PCI, and TM promotes its procoagulant function. To gain insight into how PCI recognition of thrombin is aided by these cofactors, we determined a crystallographic structure of the Michaelis complex of PCI, thrombin, and heparin to 1.6 A resolution. Thrombin interacts with PCI in an unusual fashion that depends on the length of PCI's reactive center loop (RCL) to align the heparin-binding sites of the two proteins. The principal exosite contact is engendered by movement of thrombin's 60-loop in response to the unique P2 Phe of PCI. This mechanism of communication between the active site of thrombin and its recognition exosite is previously uncharacterized and may relate to other thrombin substrate-cofactor interactions. The cofactor activity of heparin thus depends on the formation of a heparin-bridged Michaelis complex and substrate-induced exosite contacts. We also investigated the cofactor effect of TM, establishing that TM bridges PCI to thrombin through additional direct interactions. A model of the PCI-thrombin-TM complex was built and evaluated by mutagenesis and suggests distinct binding sites for heparin and TM on PCI. These data significantly improve our understanding of the cofactor-dependent roles of PCI in hemostasis.
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Complementary structural mass spectrometry techniques reveal local dynamics in functionally important regions of a metastable serpin. Structure 2008; 16:38-51. [PMID: 18184582 DOI: 10.1016/j.str.2007.10.019] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Revised: 10/19/2007] [Accepted: 10/27/2007] [Indexed: 01/10/2023]
Abstract
Serpins display a number of highly unusual structural properties along with a unique mechanism of inhibition. Although structures of numerous serpins have been solved by X-ray crystallography, little is known about the dynamics of serpins in their inhibitory active conformation. In this study, two complementary structural mass spectrometry methods, hydroxyl radical-mediated footprinting and hydrogen/deuterium (H/D) exchange, were employed to highlight differences between the static crystal structure and the dynamic conformation of human serpin protein, alpha(1)-antitrypsin (alpha(1)AT). H/D exchange revealed the distribution of flexible and rigid regions of alpha(1)AT, whereas footprinting revealed the dynamic environments of several side chains previously identified as important for the metastability of alpha(1)AT. This work provides insights into the unique structural design of alpha(1)AT and improves our understanding of its unusual inhibition mechanism. Also, we demonstrate that the combination of the two MS techniques provides a more complete picture of protein structure than either technique alone.
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29
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Zhang Q, Law RHP, Bottomley SP, Whisstock JC, Buckle AM. A structural basis for loop C-sheet polymerization in serpins. J Mol Biol 2008; 376:1348-59. [PMID: 18234218 DOI: 10.1016/j.jmb.2007.12.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 12/17/2007] [Accepted: 12/20/2007] [Indexed: 10/22/2022]
Abstract
In this study, we report the X-ray crystal structure of an N-terminally truncated variant of the bacterial serpin, tengpin (tengpinDelta42). Our data reveal that tengpinDelta42 adopts a variation of the latent conformation in which the reactive center loop is hyperinserted into the A beta-sheet and removed from the vicinity of the C-sheet. This conformational change leaves the C beta-sheet completely exposed and permits antiparallel edge-strand interactions between the exposed portion of the reactive center loop of one molecule and strand s2C of the C beta-sheet of the neighboring molecule in the crystal lattice. Our structural data thus reveal that tengpinDelta42 forms a loop C-sheet polymer in the crystal lattice. In vivo serpins have a propensity to misfold and form long-chain polymers, a process that underlies serpinopathies such as emphysema, thrombosis and dementia. Native serpins are thought to polymerize via a loop A-sheet mechanism. However, studies on plasminogen activator inhibitor 1 and the S49P variant of human neuroserpin reveal that the latent form of these molecules can also polymerize. Polymerization of latent neuroserpin may be important for the development of familial encephalopathy with neuroserpin inclusion bodies. Our structural data provide a possible mechanism for polymerization by latent serpins.
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Affiliation(s)
- Qingwei Zhang
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, VIC 3800, Australia
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30
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Askew DJ, Cataltepe S, Kumar V, Edwards C, Pace SM, Howarth RN, Pak SC, Askew YS, Brömme D, Luke CJ, Whisstock JC, Silverman GA. SERPINB11 Is a New Noninhibitory Intracellular Serpin. J Biol Chem 2007; 282:24948-60. [PMID: 17562709 DOI: 10.1074/jbc.m703182200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SERPINB11, the last of 13 human clade B serpins to be described, gave rise to seven different isoforms. One cDNA contained a premature termination codon, two contained splice variants, and four contained full-length open reading frames punctuated by eight single nucleotide polymorphisms (SNPs). The SNPs encoded amino acid variants located within the serpin scaffold but not the reactive site loop (RSL). Although the mouse orthologue, Serpinb11, could inhibit trypsin-like peptidases, SERPINB11 showed no inhibitory activity. To determine whether the human RSL targeted a different class of peptidases or the serpin scaffold was unable to support inhibitory activity, we synthesized chimeric human and mouse proteins, in which the RSLs had been swapped. The human RSL served as a trypsin inhibitor when supported by mouse scaffold sequences. Conversely, the mouse RSL on the human scaffold showed no inhibitory activity. These findings suggested that variant residues in the SERPINB11 scaffold impaired serpin function. SDS-PAGE analysis supported this notion as RSL-cleaved SERPINB11 was unable to undergo the stressed-to-relaxed transition typical of inhibitory type serpins. Mutagenesis studies supported this hypothesis, since the reversion of amino acid sequences in helices D and I to those conserved in other clade B serpins partially restored the ability of SERPINB11 to form covalent complexes with trypsin. Taken together, these findings suggested that SERPINB11 SNPs encoded amino acids in the scaffold that impaired RSL mobility, and HapMap data showed that the majority of genomes in different human populations harbored these noninhibitory SERPINB11 alleles. Like several other serpin superfamily members, SERPINB11 has lost inhibitory activity and may have evolved a noninhibitory function.
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Affiliation(s)
- David J Askew
- University of Pittsburgh Medical Center Newborn Medicine Program, Children's Hospital of Pittsburgh and Magee--Womens Research Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA
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31
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Zhang Q, Buckle AM, Law RHP, Pearce MC, Cabrita LD, Lloyd GJ, Irving JA, Smith AI, Ruzyla K, Rossjohn J, Bottomley SP, Whisstock JC. The N terminus of the serpin, tengpin, functions to trap the metastable native state. EMBO Rep 2007; 8:658-63. [PMID: 17557112 PMCID: PMC1905895 DOI: 10.1038/sj.embor.7400986] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 04/04/2007] [Accepted: 04/04/2007] [Indexed: 12/03/2022] Open
Abstract
Serpins fold to a metastable native state and are susceptible to undergoing spontaneous conformational change to more stable conformers, such as the latent form. We investigated conformational change in tengpin, an unusual prokaryotic serpin from the extremophile Thermoanaerobacter tengcongensis. In addition to the serpin domain, tengpin contains a functionally uncharacterized 56-amino-acid amino-terminal region. Deletion of this domain creates a variant—tengpinΔ51—which folds past the native state and readily adopts the latent conformation. Analysis of crystal structures together with mutagenesis studies show that the N terminus of tengpin protects a hydrophobic patch in the serpin domain and functions to trap tengpin in its native metastable state. A 13-amino-acid peptide derived from the N terminus is able to mimick the role of the N terminus in stabilizing the native state of tengpinΔ51. Therefore, the function of the N terminus in tengpin resembles protein cofactors that prevent mammalian serpins from spontaneously adopting the latent conformation.
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Affiliation(s)
- Qingwei Zhang
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Ashley M Buckle
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Ruby H P Law
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Mary C Pearce
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Lisa D Cabrita
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Gordon J Lloyd
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - James A Irving
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - A Ian Smith
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
- ARC Centre of Excellence for Structural and Functional Microbial Genomics, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Katya Ruzyla
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Jamie Rossjohn
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
- ARC Centre of Excellence for Structural and Functional Microbial Genomics, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Stephen P Bottomley
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
- Tel: +613 9905 3747; Fax: +613 9905 3703; E-mail:
| | - James C Whisstock
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Victoria 3800, Australia
- ARC Centre of Excellence for Structural and Functional Microbial Genomics, Monash University, Clayton, Melbourne, Victoria 3800, Australia
- Tel: +613 9905 3747; Fax: +613 9905 4699; E-mail:
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32
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Shin JS, Ryu SH, Lee C, Yu MH. Misfolding-assisted selection of stable protein variants using phage displays. BMB Rep 2006; 39:55-60. [PMID: 16466638 DOI: 10.5483/bmbrep.2006.39.1.055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We describe a phage display strategy, based on the differential resistance of proteins to denaturant-induced unfolding, that can be used to select protein variants with improved conformational stability. To test the efficiency of this strategy, wild-type and two stable variants of alpha1-antitrypsin (alpha1AT) were fused to the gene III protein of M13 phage. These phages were incubated in unfolding solution containing denaturant (urea or guanidinium chloride), and then subjected to an unfavorable refolding procedure (dialysis at 37 degrees C). Once the alpha1AT moiety of the fusion protein had unfolded in the unfolding solution, in which the denaturant concentration was higher than the unfolding transition midpoint (Cm) of the alpha1AT variant, around 20% of the phage retained binding affinity to anti-alpha1AT antibody due to a low refolding efficiency. Moreover, this affinity reduced to less than 5% when 10 mg/mL skimmed milk (a misfolding-promoting additive) was included during the unfolding/refolding procedure. In contrast, most binding affinity (>95%) remained if the alpha1AT variant was stable enough to resist unfolding. Because this selection procedure does not affect the infectivity of M13, the method is expected to be generally applicable to the high-throughput screening of stable protein variants, when activity-based screening is not possible.
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Affiliation(s)
- Jong-Shik Shin
- Functional Proteomics Center, Korea Institute of Science and Technology, Hawolgok-dong, Seoul 136-791, Korea
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33
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Roche O, Blanch A, Duponchel C, Fontán G, Tosi M, López-Trascasa M. Hereditary angioedema: The mutation spectrum ofSERPING1/C1NHin a large Spanish cohort. Hum Mutat 2005; 26:135-44. [PMID: 15971231 DOI: 10.1002/humu.20197] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Hereditary angioedema (HAE) is a disease caused by defects in the C1 inhibitor gene (SERPING1/C1NH). We screened the entire C1NH gene for mutations in a large series of 87 Spanish families (77 with type I, and 10 with type II HAE) by SSCP, sequencing, Southern blotting, and quantitative multiplex PCR of short fluorescent fragments (QMPSF), and we characterized several defects at the mRNA level. We found large rearrangements in 13 families, and point mutations or microdeletions/insertions in 74 families. The 13 large rearrangements included nine exon deletions, of which at least eight were distinct, two were distinct exon duplications, and two were rearrangements whose precise nature could not be determined. We confirmed that exon 4 is particularly prone to rearrangements. Thirty-six mutations were unreported, and included 10 microdeletions/insertions, 10 missense, five nonsense, eight splicing, and three splicing or missense mutations. Moreover, we detected six novel uncharacterized sequence variants (USV). RT-PCR studies showed that in addition to several intronic splice site mutations tested, the exonic mutations c.882C>G and c.884T>G, located near the 3' end of exon 5, also produced exon skipping. This is the first evidence of SERPING1/C1NH mutations in coding regions that differ from the canonical splice sites that affect splicing, which suggests the presence of an exonic splicing enhancer (ESE) in exon 5.
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Affiliation(s)
- Olga Roche
- Unidad de Inmunología, Hospital Universitario La Paz, Madrid, Spain
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34
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Law RHP, Irving JA, Buckle AM, Ruzyla K, Buzza M, Bashtannyk-Puhalovich TA, Beddoe TC, Nguyen K, Worrall DM, Bottomley SP, Bird PI, Rossjohn J, Whisstock JC. The high resolution crystal structure of the human tumor suppressor maspin reveals a novel conformational switch in the G-helix. J Biol Chem 2005; 280:22356-64. [PMID: 15760906 DOI: 10.1074/jbc.m412043200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Maspin is a serpin that acts as a tumor suppressor in a range of human cancers, including tumors of the breast and lung. Maspin is crucial for development, because homozygous loss of the gene is lethal; however, the precise physiological role of the molecule is unclear. To gain insight into the function of human maspin, we have determined its crystal structure in two similar, but non-isomorphous crystal forms, to 2.1- and 2.8-A resolution, respectively. The structure reveals that maspin adopts the native serpin fold in which the reactive center loop is expelled fully from the A beta-sheet, makes minimal contacts with the core of the molecule, and exhibits a high degree of flexibility. A buried salt bridge unique to maspin orthologues causes an unusual bulge in the region around the D and E alpha-helices, an area of the molecule demonstrated in other serpins to be important for cofactor recognition. Strikingly, the structural data reveal that maspin is able to undergo conformational change in and around the G alpha-helix, switching between an open and a closed form. This change dictates the electrostatic character of a putative cofactor binding surface and highlights this region as a likely determinant of maspin function. The high resolution crystal structure of maspin provides a detailed molecular framework to elucidate the mechanism of function of this important tumor suppressor.
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Affiliation(s)
- Ruby H P Law
- The Protein Crystallography Unit, Monash Centre for Synchrotron Science and The Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Faculty of Medicine, Monash University, Clayton, Victoria 3800, Australia
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35
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Fulton KF, Buckle AM, Cabrita LD, Irving JA, Butcher RE, Smith I, Reeve S, Lesk AM, Bottomley SP, Rossjohn J, Whisstock JC. The high resolution crystal structure of a native thermostable serpin reveals the complex mechanism underpinning the stressed to relaxed transition. J Biol Chem 2004; 280:8435-42. [PMID: 15590653 DOI: 10.1074/jbc.m410206200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Serpins fold into a native metastable state and utilize a complex conformational change to inhibit target proteases. An undesirable result of this conformational flexibility is that most inhibitory serpins are heat sensitive, forming inactive polymers at elevated temperatures. However, the prokaryote serpin, thermopin, from Thermobifida fusca is able to function in a heated environment. We have determined the 1.8 A x-ray crystal structure of thermopin in the native, inhibitory conformation. A structural comparison with the previously determined 1.5 A structure of cleaved thermopin provides detailed insight into the complex mechanism of conformational change in serpins. Flexibility in the shutter region and electrostatic interactions at the top of the A beta-sheet (the breach) involving the C-terminal tail, a unique structural feature of thermopin, are postulated to be important for controlling inhibitory activity and triggering conformational change, respectively, in the native state. Here we have discussed the structural basis of how this serpin reconciles the thermodynamic instability necessary for function with the stability required to withstand elevated temperatures.
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Affiliation(s)
- Kate F Fulton
- Protein Crystallography Unit, Monash Centre for Synchrotron Science, Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Faculty of Medicine, Victorian Bioinformatics Consortium, P. O. Box 53, Australia
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36
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Ikeda K, Higo J. Free-energy landscape of a chameleon sequence in explicit water and its inherent alpha/beta bifacial property. Protein Sci 2004; 12:2542-8. [PMID: 14573865 PMCID: PMC2366969 DOI: 10.1110/ps.03143803] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A sequence in yeast MATalpha2/MCM1/DNA complex that folds into alpha-helix or beta-hairpin depending on the surroundings has been known as "chameleon" sequence. We obtained the free-energy landscape of this sequence by using a generalized-ensemble method, multicanonical molecular dynamics simulation, to sample the conformational space. The system was expressed with an all-atom model in explicit water, and the initial conformation for the simulation was a random one. The free-energy landscape demonstrated that this sequence inherently has an ability to form either alpha or beta structure: The conformational distribution in the landscape consisted of two alpha-helical clusters with different packing patterns of hydrophobic residues, and four beta-hairpin clusters with different strand-strand interaction patterns. Narrow pathways connecting the clusters were found, and analysis on the pathways showed that a compact structure formed at the N-terminal root of the chameleon sequence controls the cluster-cluster transitions. The free-energy landscape indicates that a small conditional change induces alpha-beta transitions. Additional unfolding simulations done with replacing amino acids showed that the chameleon sequence has an advantage to form an alpha-helix. Current study may be useful to understand the mechanism of diseases resulting from abnormal chain folding, such as amyloid disease.
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Affiliation(s)
- Kazuyoshi Ikeda
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology, Koto-ku, Tokyo 135-0064, Japan
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37
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Corral J, Huntington JA, González-Conejero R, Mushunje A, Navarro M, Marco P, Vicente V, Carrell RW. Mutations in the shutter region of antithrombin result in formation of disulfide-linked dimers and severe venous thrombosis. J Thromb Haemost 2004; 2:931-9. [PMID: 15140129 DOI: 10.1111/j.1538-7836.2004.00749.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Missense mutations causing conformational alterations in serpins can be responsible for protein deficiency associated with human diseases. However, there are few data about conformational consequences of mutations affecting antithrombin, the main hemostatic serpin. OBJECTIVES To investigate the conformational and clinical effect of mutations affecting the shutter region of antithrombin. PATIENTS AND METHODS We identified two families with significant reduction of circulating antithrombin displaying early and severe venous thrombosis, frequently associated with pregnancy or infection. Mutations were determined by standard molecular methods. Biochemical studies were performed on plasma samples. One variant (P80S) was purified by heparin-affinity chromatography and gel filtration, and evaluated by proteomic analysis. Finally, we modelled the structure of the mutant dimer. RESULTS We identified two missense mutations affecting the shutter region of antithrombin: P80S and G424R. Carriers of both mutations presented traces of a similar abnormal antithrombin, supporting inefficiently expressed rather than non-expressed variants. The abnormal antithrombin purified from P80S carriers is an inactive disulfide-linked dimer of mutant antithrombin whose properties are consistent with head-to-head insertion of the reactive loop. CONCLUSIONS Our data support the conclusion that missense mutations affecting the shutter region of serpins have specific conformational effects resulting in the formation of mutant oligomers. The consequent inefficiency of secretion explains the accompanying deficiency and loss of function, but the severity of thrombosis associated with these mutations suggests that the oligomers also have new and undefined pathological properties that could be exacerbated by pregnancy or infection.
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Affiliation(s)
- J Corral
- Department of Medicine, University of Murcia, Murcia, Spain.
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38
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Krem MM, Di Cera E. Conserved Ser residues, the shutter region, and speciation in serpin evolution. J Biol Chem 2003; 278:37810-4. [PMID: 12847097 DOI: 10.1074/jbc.m305088200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The suicide inhibitory mechanism of serine protease inhibitors of the serpin superfamily depends heavily on their structural flexibility, which is controlled in large part by the breach and shutter regions of the central Abeta-sheet. We examined codon usage by the highly conserved residues, Ser-53 and Ser-56, of the shutter region and found a TCN-AGY usage dichotomy for Ser-56 that remarkably is linked to the protostome-deuterostome split. Our results suggest that serpin evolution was driven by phylogenetic speciation and not pressure to fulfill new physiologic functions mitigating against coevolution with the family of serine proteases they inhibit.
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Affiliation(s)
- Maxwell M Krem
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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39
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Zhou A, Stein PE, Huntington JA, Carrell RW. Serpin polymerization is prevented by a hydrogen bond network that is centered on his-334 and stabilized by glycerol. J Biol Chem 2003; 278:15116-22. [PMID: 12578831 DOI: 10.1074/jbc.m211663200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polymerization of serpins commonly results from mutations in the shutter region underlying the bifurcation of strands 3 and 5 of the A-sheet, with entry beyond this point being barred by a H-bond network centered on His-334. Exposure of this histidine in antithrombin, which has a partially opened sheet, allows polymerization and peptide insertion to occur at pH 6 or less when His-334 will be predictably protonated with disruption of the H-bond network. Similarly, thermal stability of antithrombin is pH-dependent with a single unfolding transition at pH 6, but there is no such transition when His-334 is buried by a fully closed A-sheet in heparin-complexed antithrombin or in alpha(1)-antitrypsin. Replacement of His-334 in alpha(1)-antitrypsin by a serine or alanine at pH 7.4 results in the same polymerization and loop-peptide acceptance observed with antithrombin at low pH. The critical role of His-334 and the re-formation of its H-bond network by the conserved P8 threonine, on the full insertion of strand 4, are relevant for the design of therapeutic blocking agents. This is highlighted here by the crystallographic demonstration that glycerol, which at high concentrations blocks polymerization, can replace the P8 threonine and re-form the disrupted H-bond network with His-334.
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Affiliation(s)
- Aiwu Zhou
- Department of Haematology, University of Cambridge, Cambridge Institute of Medical Research, Hills Road, Cambridge CB2 2XY, United Kingdom.
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40
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Wilczynska M, Lobov S, Ohlsson PI, Ny T. A redox-sensitive loop regulates plasminogen activator inhibitor type 2 (PAI-2) polymerization. EMBO J 2003; 22:1753-61. [PMID: 12682008 PMCID: PMC154470 DOI: 10.1093/emboj/cdg178] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Plasminogen activator inhibitor type 2 (PAI-2) is the only wild-type serpin that polymerizes spontaneously under physiological conditions. We show that PAI-2 loses its ability to polymerize following reduction of thiol groups, suggesting that an intramolecular disulfide bond is essential for the polymerization. A novel disulfide bond was identified between C79 (in the CD-loop) and C161 (at the bottom of helix F). Substitution mutants in which this disulfide bond was broken did not polymerize. Reactive center loop peptide insertion experiments and binding of bis-ANS to hydrophobic cavities indicate that the C79-C161 disulfide bond stabilizes PAI-2 in a polymerogenic conformation with an open A-beta-sheet. Elimination of this disulfide bond causes A-beta-sheet closure and abrogates the polymerization. The finding that cytosolic PAI-2 is mostly monomeric, whereas PAI-2 in the secretory pathway is prone to polymerize, suggests that the redox status of the cell could regulate PAI-2 polymerization. Taken together, our data suggest that the CD-loop functions as a redox-sensitive switch that converts PAI-2 between an active stable monomeric and a polymerogenic conformation, which is prone to form inactive polymers.
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Affiliation(s)
- Malgorzata Wilczynska
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
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41
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Irving JA, Cabrita LD, Rossjohn J, Pike RN, Bottomley SP, Whisstock JC. The 1.5 A crystal structure of a prokaryote serpin: controlling conformational change in a heated environment. Structure 2003; 11:387-97. [PMID: 12679017 DOI: 10.1016/s0969-2126(03)00057-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Serpins utilize conformational change to inhibit target proteinases; the price paid for this conformational flexibility is that many undergo temperature-induced polymerization. Despite this thermolability, serpins are present in the genomes of thermophilic prokaryotes, and here we characterize the first such serpin, thermopin. Thermopin is a proteinase inhibitor and, in comparison with human alpha(1)-antitrypsin, possesses enhanced stability at 60 degrees C. The 1.5 A crystal structure reveals novel structural features in regions implicated in serpin folding and stability. Thermopin possesses a C-terminal "tail" that interacts with the top of the A beta sheet and plays an important role in the folding/unfolding of the molecule. These data provide evidence as to how this unusual serpin has adapted to fold and function in a heated environment.
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Affiliation(s)
- James A Irving
- The Protein Crystallography Unit, Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, 3800, Clayton, Australia
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42
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Wind T, Jensen JK, Dupont DM, Kulig P, Andreasen PA. Mutational analysis of plasminogen activator inhibitor-1. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1680-8. [PMID: 12694181 DOI: 10.1046/j.1432-1033.2003.03524.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The serpin plasminogen activator inhibitor-1 (PAI-1) is a fast and specific inhibitor of the plasminogen activating serine proteases tissue-type and urokinase-type plasminogen activator and, as such, an important regulator in turnover of extracellular matrix and in fibrinolysis. PAI-1 spontaneously loses its antiproteolytic activity by inserting its reactive centre loop (RCL) as strand 4 in beta-sheet A, thereby converting to the so-called latent state. We have investigated the importance of the amino acid sequence of alpha-helix F (hF) and the connecting loop to s3A (hF/s3A-loop) for the rate of latency transition. We grafted regions of the hF/s3A-loop from antithrombin III and alpha1-protease inhibitor onto PAI-1, creating eight variants, and found that one of these reversions towards the serpin consensus decreased the rate of latency transition. We prepared 28 PAI-1 variants with individual residues in hF and beta-sheet A replaced by an alanine. We found that mutating serpin consensus residues always had functional consequences whereas mutating nonconserved residues only had so in one case. Two variants had low but stable inhibitory activity and a pronounced tendency towards substrate behaviour, suggesting that insertion of the RCL is held back during latency transition as well as during complex formation with target proteases. The data presented identify new determinants of PAI-1 latency transition and provide general insight into the characteristic loop-sheet interactions in serpins.
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Affiliation(s)
- Troels Wind
- Laboratory of Cellular Protein Science, Department of Molecular Biology, Aarhus University, Denmark
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Davis RL, Shrimpton AE, Carrell RW, Lomas DA, Gerhard L, Baumann B, Lawrence DA, Yepes M, Kim TS, Ghetti B, Piccardo P, Takao M, Lacbawan F, Muenke M, Sifers RN, Bradshaw CB, Kent PF, Collins GH, Larocca D, Holohan PD. Association between conformational mutations in neuroserpin and onset and severity of dementia. Lancet 2002; 359:2242-7. [PMID: 12103288 DOI: 10.1016/s0140-6736(02)09293-0] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND The aggregation of specific proteins is a common feature of the familial dementias, but whether the formation of neuronal inclusion bodies is a causative or incidental factor in the disease is not known. To clarify this issue, we investigated five families with typical neuroserpin inclusion bodies but with various neurological manifestations. METHODS Five families with neurodegenerative disease and typical neuronal inclusions had biopsy or autopsy material available for further examination. Immunostaining confirmed that the inclusions were formed of neuroserpin aggregates, and the responsible mutations in neuroserpin were identified by sequencing of the neuroserpin gene (SERPINI1) in DNA from blood samples or from extraction of histology specimens. Molecular modelling techniques were used to predict the effect of the gene mutations on three-dimensional protein structure. Brain sections were stained and the topographic distribution of the neuroserpin inclusions plotted. FINDINGS Each of the families was heterozygous for an amino acid substitution that affected the conformational stability of neuroserpin. The least disruptive of these mutations (S49P), as predicted by molecular modelling, resulted in dementia after age 45 years, and presence of neuroserpin inclusions in only a few neurons. By contrast, the most severely disruptive mutation (G392E) resulted, at age 13 years, in progressive myoclonus epilepsy, with many inclusions present in almost all neurons. INTERPRETATION The findings provide evidence that inclusion-body formation is in itself a sufficient cause of neurodegeneration, and that the onset and severity of the disease is associated with the rate and magnitude of neuronal protein aggregation.
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Affiliation(s)
- Richard L Davis
- Department of Pathology, Upstate Medical University, Syracuse, NY, USA
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Wind T, Hansen M, Jensen JK, Andreasen PA. The molecular basis for anti-proteolytic and non-proteolytic functions of plasminogen activator inhibitor type-1: roles of the reactive centre loop, the shutter region, the flexible joint region and the small serpin fragment. Biol Chem 2002; 383:21-36. [PMID: 11928815 DOI: 10.1515/bc.2002.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The serine proteinase inhibitor plasminogen activator inhibitor type-1 (PAI-1) is the primary physiological inhibitor of the tissue-type and the urokinase-type plasminogen activator (tPA and uPA, respectively) and as such an important regulator of proteolytic events taking place in the circulation and in the extracellular matrix. Moreover, a few non-proteolytic functions have been ascribed to PAI-1, mediated by its interaction with vitronectin or the interaction between the uPA-PAI-1 complex bound to the uPA receptor and members of the low density lipoprotein receptor family. PAI-1 belongs to the serpin family, characterised by an unusual conformational flexibility, which governs its molecular interactions. In this review we describe the anti-proteolytic and non-proteolytic functions of PAI-1 from both a biological and a biochemical point of view. We will relate the various biological roles of PAI-1 to its biochemistry in general and to the different conformations of PAI-1 in particular. We put emphasis on the intramolecular rearrangements of PAI-1 that are required for its antiproteolytic as well as its non-proteolytic functions.
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Affiliation(s)
- Troels Wind
- Department of Molecular and Structural Biology, Aarhus University, Denmark
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45
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Jankova L, Harrop SJ, Saunders DN, Andrews JL, Bertram KC, Gould AR, Baker MS, Curmi PM. Crystal structure of the complex of plasminogen activator inhibitor 2 with a peptide mimicking the reactive center loop. J Biol Chem 2001; 276:43374-82. [PMID: 11546761 DOI: 10.1074/jbc.m103021200] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The structure of the serpin, plasminogen activator inhibitor type-2 (PAI-2), in a complex with a peptide mimicking its reactive center loop (RCL) has been determined at 1.6-A resolution. The structure shows the relaxed state serpin structure with a prominent six-stranded beta-sheet. Clear electron density is seen for all residues in the peptide. The P1 residue of the peptide binds to a well defined pocket at the base of PAI-2 that may be important in determining the specificity of protease inhibition. The stressed-to-relaxed state (S --> R) transition in PAI-2 can be modeled as the relative motion between a quasirigid core domain and a smaller segment comprising helix hF and beta-strands s1A, s2A, and s3A. A comparison of the Ramachandran plots of the stressed and relaxed state PAI-2 structures reveals the location of several hinge regions connecting these two domains. The hinge regions cluster in three locations on the structure, ensuring a cooperative S --> R transition. We hypothesize that the hinge formed by the conserved Gly(206) on beta-strand s3A in the breach region of PAI-2 effects the S --> R transition by altering its backbone torsion angles. This torsional change is due to the binding of the P14 threonine of the RCL to the open breach region of PAI-2.
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Affiliation(s)
- L Jankova
- Initiative in Biomolecular Structure, School of Physics, University of New South Wales, Sydney New South Wales 2052, Australia
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46
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Boudier C, Bieth JG. The reaction of serpins with proteinases involves important enthalpy changes. Biochemistry 2001; 40:9962-7. [PMID: 11502192 DOI: 10.1021/bi010701o] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
When active serpins are proteolytically inactivated in a substrate-like reaction, they undergo an important structural transition with a resultant increase in their conformational stability. We have used microcalorimetry to show that this conformational alteration is accompanied by an important enthalpy change. For instance, the cleavage of alpha(1)-proteinase inhibitor by Pseudomonas aeruginosa elastase, Staphylococcus aureus V8 proteinase, or papain and that of antithrombin by leukocyte elastase are characterized by large enthalpy changes (DeltaH = -53 to -63 kcal mol(-1)). The former reaction also has a large and negative heat capacity (DeltaC(p)() = -566 cal K(-1) mol(-1)). In contrast, serpins release significantly less heat when they act as proteinase inhibitors. For example, the inhibition of pancreatic elastase, leukocyte elastase, and pancreatic chymotrypsin by alpha(1)-proteinase inhibitor and that of pancreatic trypsin and coagulation factor Xa by antithrombin are accompanied by a DeltaH of -20 to -31 kcal mol(-1). We observe no heat release upon proteolytic cleavage of inactive serpins or following inhibition of serine proteinases by canonical inhibitors or upon acylation of chymotrypsin by N-trans-cinnamoylimidazole. We suggest that part of the large enthalpy change that occurs during the structural transition of serpins is used to stabilize the proteinase in its inactive state.
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Affiliation(s)
- C Boudier
- Laboratoire d'Enzymologie, INSERM Unité 392, Université Louis Pasteur de Strasbourg, F-67400 Illkirch, France
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47
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O'Malley KM, Cooperman BS. Formation of the covalent chymotrypsin.antichymotrypsin complex involves no large-scale movement of the enzyme. J Biol Chem 2001; 276:6631-9. [PMID: 11027695 DOI: 10.1074/jbc.m008478200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
alpha(1)-Antichymotrypsin is a member of the serine proteinase inhibitor, or serpin, family that typically forms very long-lived, enzymatically inactive 1:1 complexes (denoted E*I*) with its target proteinases. Serpins share a conserved tertiary structure, in which an exposed region of amino acid residues (called the reactive center loop or RCL) acts as bait for a target proteinase. Within E*I*, the two proteins are linked covalently as a result of nucleophilic attack by Ser(195) of the serine proteinase on the P1 residue within the RCL of the serpin. This species is formally similar to the acyl enzyme species normally seen as an intermediate in serpin proteinase catalysis. However, its subsequent hydrolysis is extremely slow as a result of structural changes within the enzyme leading to distortion of the active site. There is at present an ongoing debate concerning the structure of the E*I* complex; in particular, as to whether the enzyme, bound to P1, maintains its original position at the top of the serpin molecule or instead translocates across the entire length of the serpin, with concomitant insertion of RCL residues P1-P14 within beta-sheet A and a large separation of the enzyme and RCL residue P1'. We report time-resolved fluorescence energy transfer and rapid mixing/quench studies that support the former model. Our results indicate that the distance between residue P1' in alpha(1)-antichymotrypsin and the amino terminus of chymotrypsin actually decreases on conversion of the encounter complex E.I to E*I*. These results led us to formulate a comprehensive mechanism that accounted both for our results and for those of others supporting the two different E*I* structures. In this mechanism, partial insertion of the RCL, with no large perturbation of the P1' enzyme distance, is followed by covalent acyl enzyme formation. Full insertion can subsequently take place, in a reversible fashion, with the position of equilibrium between the partially and fully inserted complexes depending on the particular serpin-proteinase pair under consideration.
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Affiliation(s)
- K M O'Malley
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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48
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Stoop AA, Eldering E, Dafforn TR, Read RJ, Pannekoek H. Different structural requirements for plasminogen activator inhibitor 1 (PAI-1) during latency transition and proteinase inhibition as evidenced by phage-displayed hypermutated PAI-1 libraries. J Mol Biol 2001; 305:773-83. [PMID: 11162091 DOI: 10.1006/jmbi.2000.4356] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plasminogen activator inhibitor type 1 (PAI-1) is a member of the serine protease inhibitor (serpin) superfamily. Its highly mobile reactive-center loop (RCL) is thought to account for both the rapid inhibition of tissue-type plasminogen activator (t-PA), and the rapid and spontaneous transition of the unstable, active form of PAI-1 into a stable, inactive (latent) conformation (t(1/2) at 37 degrees C, 2.2 hours). We determined the amino acid residues responsible for the inherent instability of PAI-1, to assess whether these properties are independent and, consequently, whether the structural basis for inhibition and latency transition is different. For that purpose, a hypermutated PAI-1 library that is displayed on phage was pre-incubated for increasing periods (20 to 72 hours) at 37 degrees C, prior to a stringent selection for rapid t-PA binding. Accordingly, four rounds of phage-display selection resulted in the isolation of a stable PAI-1 variant (st-44: t(1/2) 450 hours) with 11 amino acid mutations. Backcrossing by DNA shuffling of this stable mutant with wt PAI-1 was performed to eliminate non-contributing mutations. It was shown that the combination of mutations at positions 50, 56, 61, 70, 94, 150, 222, 223, 264 and 331 increases the half-life of PAI-1 245-fold. Furthermore, within the limits of detection the stable mutants isolated are functionally indistinguishable from wild-type PAI-1 with respect to the rate of inhibition of t-PA, cleavage by t-PA, and binding to vitronectin. These stabilizing mutations constitute largely reversions to the stable "serpin consensus sequence" and are located in areas implicated in PAI-1 stability (e.g. the vitronectin-binding domain and the proximal hinge). Collectively, our data provide evidence that the structural requirements for PAI-1 loop insertion during latency transition and target proteinase inhibition can be separated.
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Affiliation(s)
- A A Stoop
- Department of Biochemistry Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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49
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Metzler DE, Metzler CM, Sauke DJ. Transferring Groups by Displacement Reactions. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50015-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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50
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Irving JA, Pike RN, Lesk AM, Whisstock JC. Phylogeny of the Serpin Superfamily: Implications of Patterns of Amino Acid Conservation for Structure and Function. Genome Res 2000. [DOI: 10.1101/gr.147800] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We present a comprehensive alignment and phylogenetic analysis of the serpins, a superfamily of proteins with known members in higher animals, nematodes, insects, plants, and viruses. We analyze, compare, and classify 219 proteins representative of eight major and eight minor subfamilies, using a novel technique of consensus analysis. Patterns of sequence conservation characterize the family as a whole, with a clear relationship to the mechanism of function. Variations of these patterns within phylogenetically distinct groups can be correlated with the divergence of structure and function. The goals of this work are to provide a carefully curated alignment of serpin sequences, to describe patterns of conservation and divergence, and to derive a phylogenetic tree expressing the relationships among the members of this family. We extend earlier studies by Huber and Carrell as well as by Marshall, after whose publication the serpin family has grown functionally, taxonomically, and structurally. We used gene and protein sequence data, crystal structures, and chromosomal location where available. The results illuminate structure–function relationships in serpins, suggesting roles for conserved residues in the mechanism of conformational change. The phylogeny provides a rational evolutionary framework to classify serpins and enables identification of conserved amino acids. Patterns of conservation also provide an initial point of comparison for genes identified by the various genome projects. New homologs emerging from sequencing projects can either take their place within the current classification or, if necessary, extend it.
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