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Yildiz P, Ozcan S. A single protein to multiple peptides: Investigation of protein-peptide correlations using targeted alpha-2-macroglobulin analysis. Talanta 2023; 265:124878. [PMID: 37392709 DOI: 10.1016/j.talanta.2023.124878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 04/30/2023] [Accepted: 06/22/2023] [Indexed: 07/03/2023]
Abstract
Recent advances in proteomics technologies have enabled the analysis of thousands of proteins in a high-throughput manner. Mass spectrometry (MS) based proteomics uses a peptide-centric approach where biological samples undergo specific proteolytic digestion and then only unique peptides are used for protein identification and quantification. Considering the fact that a single protein may have multiple unique peptides and a number of different forms, it becomes essential to understand dynamic protein-peptide relationships to ensure robust and reliable peptide-centric protein analysis. In this study, we investigated the correlation between protein concentration and corresponding unique peptide responses under a conventional proteolytic digestion condition. Protein-peptide correlation, digestion efficiency, matrix-effect, and concentration-effect were evaluated. Twelve unique peptides of alpha-2-macroglobulin (A2MG) were monitored using a targeted MS approach to acquire insights into protein-peptide dynamics. Although the peptide responses were reproducible between replicates, protein-peptide correlation was moderate in protein standards and low in complex matrices. The results suggest that reproducible peptide signal could be misleading in clinical studies and a peptide selection could dramatically change the outcome at protein level. This is the first study investigating quantitative protein-peptide correlations in biological samples using all unique peptides representing the same protein and opens a discussion on peptide-based proteomics.
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Affiliation(s)
- Pelin Yildiz
- Department of Chemistry, Middle East Technical University (METU), 06800, Ankara, Turkiye; Nanografi Nanotechnology Co, Middle East Technical University (METU) Technopolis, 06531, Ankara, Turkiye
| | - Sureyya Ozcan
- Department of Chemistry, Middle East Technical University (METU), 06800, Ankara, Turkiye; Cancer Systems Biology Laboratory (CanSyL), Middle East Technical University (METU), 06800, Ankara, Turkiye.
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2
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Nie X, He Q, Zhou B, Huang D, Chen J, Chen Q, Yang S, Yu X. Exploring the five-paced viper ( Deinagkistrodon acutus) venom proteome by integrating a combinatorial peptide ligand library approach with shotgun LC-MS/MS. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20200196. [PMID: 34745239 PMCID: PMC8547348 DOI: 10.1590/1678-9199-jvatitd-2020-0196] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 03/18/2021] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Snake venoms are complex mixtures of toxic proteins or peptides encoded by various gene families that function synergistically to incapacitate prey. In the present study, in order to unravel the proteomic repertoire of Deinagkistrodon acutus venom, some trace abundance components were analyzed. METHODS Shotgun proteomic approach combined with shotgun nano-LC-ESI-MS/MS were employed to characterize the medically important D. acutus venom, after collected samples were enriched with the combinatorial peptide ligand library (CPLL). RESULTS This avenue helped us find some trace components, undetected before, in D. acutus venom. The results indicated that D. acutus venom comprised 84 distinct proteins from 10 toxin families and 12 other proteins. These results are more than twice the number of venom components obtained from previous studies, which were only 29 distinct proteins obtained through RP-HPLC for the venom of the same species. The present results indicated that in D. acutus venom, the most abundant components (66.9%) included metalloproteinases, serine proteinases, and C-type lectin proteins; the medium abundant components (13%) comprised phospholipases A2 (PLA2) and 5'-nucleotidases and nucleases; whereas least abundant components (6%) were aminopeptidases, L-amino acid oxidases (LAAO), neurotoxins and disintegrins; and the trace components. The last were undetected before the use of conventional shotgun proteomics combined with shotgun nano-LC-ESI-MS/MS, such as cysteine-rich secretory proteins Da-CRPa, phospholipases B-like 1, phospholipases B (PLB), nerve growth factors (NGF), glutaminyl-peptide cyclortransferases (QC), and vascular non-inflammatory molecules 2 (VNN2). CONCLUSION These findings demonstrated that the CPLL enrichment method worked well in finding the trace toxin proteins in D. acutus venom, in contrast with the previous venomic characterization of D. acutus by conventional LC-MS/MS. In conclusion, this approach combined with the CPLL enrichment was effective for allowing us to explore the hidden D. acutus venomic profile and extended the list of potential venom toxins.
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Affiliation(s)
- Xuekui Nie
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
| | - Qiyi He
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
| | - Bin Zhou
- Library, Chongqing Normal University, Chongqing, China
| | - Dachun Huang
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
| | - Junbo Chen
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
| | - Qianzi Chen
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
| | - Shuqing Yang
- Emergency Department, Chongqing Emergency Medical Center, Chongqing University Central Hospital, Chongqing, China
| | - Xiaodong Yu
- Animal Toxin Group, Engineering Research Center of Active Substance and Biotechnology, Ministry of Education, College of Life Sciences, Chongqing Normal University, Chongqing, China
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Xu C, Wang YN, Wu H. Glutaminyl Cyclase, Diseases, and Development of Glutaminyl Cyclase Inhibitors. J Med Chem 2021; 64:6549-6565. [PMID: 34000808 DOI: 10.1021/acs.jmedchem.1c00325] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pyroglutamate (pE) modification, catalyzed mainly by glutaminyl cyclase (QC), is prevalent throughout nature and is particularly important in mammals including humans for the maturation of hormones, peptides, and proteins. In humans, the upregulation of QC is involved in multiple diseases and conditions including Alzheimer's disease, Huntington's disease, melanomas, thyroid carcinomas, accelerated atherosclerosis, septic arthritics, etc. This upregulation catalyzes the generation of modified mediators such as pE-amyloid beta (Aß) and pE-chemokine ligand 2 (CCL2) peptides. Not surprisingly, QC has emerged as a reasonable target for the development of therapeutics to combat these diseases and conditions. In this manuscript the deleterious effects of upregulated QC resulting in disease manifestation are reviewed, along with progress on the development of QC inhibitors.
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Affiliation(s)
- Chenshu Xu
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Yi-Nan Wang
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen 518060, China
| | - Haiqiang Wu
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen 518060, China
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Shih YP, Chou CC, Chen YL, Huang KF, Wang AHJ. Linked production of pyroglutamate-modified proteins via self-cleavage of fusion tags with TEV protease and autonomous N-terminal cyclization with glutaminyl cyclase in vivo. PLoS One 2014; 9:e94812. [PMID: 24733552 PMCID: PMC3986218 DOI: 10.1371/journal.pone.0094812] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 03/19/2014] [Indexed: 12/28/2022] Open
Abstract
Overproduction of N-terminal pyroglutamate (pGlu)-modified proteins utilizing Escherichia coli or eukaryotic cells is a challenging work owing to the fact that the recombinant proteins need to be recovered by proteolytic removal of fusion tags to expose the N-terminal glutaminyl or glutamyl residue, which is then converted into pGlu catalyzed by the enzyme glutaminyl cyclase. Herein we describe a new method for production of N-terminal pGlu-containing proteins in vivo via intracellular self-cleavage of fusion tags by tobacco etch virus (TEV) protease and then immediate N-terminal cyclization of passenger target proteins by a bacterial glutaminyl cyclase. To combine with the sticky-end PCR cloning strategy, this design allows the gene of target proteins to be efficiently inserted into the expression vector using two unique cloning sites (i.e., SnaB I and Xho I), and the soluble and N-terminal pGlu-containing proteins are then produced in vivo. Our method has been successfully applied to the production of pGlu-modified enhanced green fluorescence protein and monocyte chemoattractant proteins. This design will facilitate the production of protein drugs and drug target proteins that possess an N-terminal pGlu residue required for their physiological activities.
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Affiliation(s)
- Yan-Ping Shih
- Institute of Biological Chemistry and Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
| | - Chi-Chi Chou
- Institute of Biological Chemistry and Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
| | - Yi-Ling Chen
- Institute of Biological Chemistry and Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
| | - Kai-Fa Huang
- Institute of Biological Chemistry and Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
- * E-mail: (AHJW); (KFH)
| | - Andrew H.- J. Wang
- Institute of Biological Chemistry and Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
- * E-mail: (AHJW); (KFH)
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5
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Chen LC, Chung YC, Chang CT. Characterisation of an acidic peroxidase from papaya (Carica papaya L. cv Tainung No. 2) latex and its application in the determination of micromolar hydrogen peroxide in milk. Food Chem 2012; 135:2529-35. [DOI: 10.1016/j.foodchem.2012.06.106] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 06/23/2012] [Accepted: 06/30/2012] [Indexed: 11/17/2022]
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Proc JL, Kuzyk MA, Hardie DB, Yang J, Smith DS, Jackson AM, Parker CE, Borchers CH. A quantitative study of the effects of chaotropic agents, surfactants, and solvents on the digestion efficiency of human plasma proteins by trypsin. J Proteome Res 2010; 9:5422-37. [PMID: 20722421 DOI: 10.1021/pr100656u] [Citation(s) in RCA: 262] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Plasma biomarkers studies are based on the differential expression of proteins between different treatment groups or between diseased and control populations. Most mass spectrometry-based methods of protein quantitation, however, are based on the detection and quantitation of peptides, not intact proteins. For peptide-based protein quantitation to be accurate, the digestion protocols used in proteomic analyses must be both efficient and reproducible. There have been very few studies, however, where plasma denaturation/digestion protocols have been compared using absolute quantitation methods. In this paper, 14 combinations of heat, solvent [acetonitrile, methanol, trifluoroethanol], chaotropic agents [guanidine hydrochloride, urea], and surfactants [sodium dodecyl sulfate (SDS) and sodium deoxycholate (DOC)] were compared with respect to their effectiveness in improving subsequent tryptic digestion. These digestion protocols were evaluated by quantitating the production of proteotypic tryptic peptides from 45 moderate- to high-abundance plasma proteins, using tandem mass spectrometry in multiple reaction monitoring mode, with a mixture of stable-isotope labeled analogues of these proteotypic peptides as internal standards. When the digestion efficiencies of these 14 methods were compared, we found that both of the surfactants (SDS and DOC) produced an increase in the overall yield of tryptic peptides from these 45 proteins, when compared to the more commonly used urea protocol. SDS, however, can be a serious interference for subsequent mass spectrometry. DOC, on the other hand, can be easily removed from the samples by acid precipitation. Examining the results of a reproducibility study, done with 5 replicate digestions, DOC and SDS with a 9 h digestion time produced the highest average digestion efficiencies (∼80%), with the highest average reproducibility (<5% error, defined as the relative deviation from the mean value). However, because of potential interferences resulting from the use of SDS, we recommend DOC with a 9 h digestion procedure as the optimum protocol.
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Affiliation(s)
- Jennifer L Proc
- University of Victoria-Genome BC Proteomics Centre, Victoria, BC, Canada
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7
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Huang WL, Wang YR, Ko TP, Chia CY, Huang KF, Wang AHJ. Crystal Structure and Functional Analysis of the Glutaminyl Cyclase from Xanthomonas campestris. J Mol Biol 2010; 401:374-88. [DOI: 10.1016/j.jmb.2010.06.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 05/31/2010] [Accepted: 06/05/2010] [Indexed: 01/14/2023]
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8
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Cornell HJ, Doherty W, Stelmasiak T. Papaya latex enzymes capable of detoxification of gliadin. Amino Acids 2009; 38:155-65. [PMID: 19156482 DOI: 10.1007/s00726-008-0223-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 12/02/2008] [Indexed: 10/21/2022]
Abstract
Assay of fractions obtained from ion exchange chromatography of papaya latex on CM Sephadex-C50, size exclusion chromatography on Sephacryl S-300 and size exclusion HPLC have provided an insight into the relative contributions of the gluten-detoxifying enzymes present. This outcome has been achieved by the use of the above chromatographic techniques, coupled with assays of lysosomal activity, protease activity using benzylarginine ethyl ester (BAEE) as substrate, prolyl endopeptidase (PEP) using glycylprolylnitroanilide and a prolidase assay using acetylprolylglycine. These procedures have shown that the activity in papaya latex is due largely to caricain and to a lesser extent, chymopapain and glutamine cyclotransferase. The presence of caricain and these other enzymes was confirmed by mass spectrometry of trypsin digests of the most active fraction obtained by CM Sephadex-C50 chromatography and size exclusion HPLC. Fractions rich in caricain would be suitable for enzyme therapy in gluten intolerance and appear to have synergistic action with porcine intestinal extracts.
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Affiliation(s)
- H J Cornell
- School of Applied Sciences, RMIT University, Melbourne, VIC, 3001, Australia.
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9
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10
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Schilling S, Wasternack C, Demuth HU. Glutaminyl cyclases from animals and plants: a case of functionally convergent protein evolution. Biol Chem 2008. [DOI: 10.1515/bc.2008.111_bchm.just-accepted] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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11
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Schilling S, Wasternack C, Demuth HU. Glutaminyl cyclases from animals and plants: a case of functionally convergent protein evolution. Biol Chem 2008; 389:983-91. [DOI: 10.1515/bc.2008.111] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractSeveral mammalian peptide hormones and proteins from plant and animal origin contain an N-terminal pyroglutamic acid (pGlu) residue. Frequently, the moiety is important in exerting biological function in either mediating interaction with receptors or stabilizing against N-terminal degradation. Glutaminyl cyclases (QCs) were isolated from different plants and animals catalyzing pGlu formation. The recent resolution of the 3D structures ofCarica papayaand human QCs clearly supports different evolutionary origins of the proteins, which is also reflected by different enzymatic mechanisms. The broad substrate specificity is revealed by the heterogeneity of physiological substrates of plant and animal QCs, including cytokines, matrix proteins and pathogenesis-related proteins. Moreover, recent evidence also suggests human QC as a catalyst of pGlu formation at the N-terminus of amyloid peptides, which contribute to Alzheimer's disease. Obviously, owing to its biophysical properties, the function of pGlu in plant and animal proteins is very similar in terms of stabilizing or mediating protein and peptide structure. It is possible that the requirement for catalysis of pGlu formation under physiological conditions may have triggered separate evolution of QCs in plants and animals.
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12
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Lin Y, Zhou J, Bi D, Chen P, Wang X, Liang S. Sodium-deoxycholate-assisted tryptic digestion and identification of proteolytically resistant proteins. Anal Biochem 2008; 377:259-66. [PMID: 18384734 DOI: 10.1016/j.ab.2008.03.009] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 03/07/2008] [Accepted: 03/07/2008] [Indexed: 11/17/2022]
Abstract
Identification of proteolytically resistant proteins with compact molecular structure and/or poor water solubility is a challenge in current proteomic study. In this study, sodium deoxycholate (SDC)-assisted tryptic digestion and identification of proteolytically resistant myoglobin and integral membrane proteins were systematically investigated. When the effect of SDC up to 10% on trypsin activity was investigated, little decrease in the trypsin activity was observed in 1% SDC solution, 2-5% SDC decreased the enzyme activity only by about 13.6%, and even in the presence of 10% SDC trypsin still retained 77.4% of its activity. Matrix-assisted laser desorption ionization time of flight mass spectrometry analysis showed that SDC could be removed from sample solution with acid treatment followed by centrifugation, and the remaining SDC, if any, had little effect on mass spectrometry analysis with regard to the number and signal/noise ratio of ions in the mass spectra. Compared with urea and methanol, two other commonly used additives in addition to SDS in proteomic analysis, SDC improved more efficiently the denaturation, solubilization, and tryptic digestion of proteins, particularly proteolytically resistant myoglobin and integral membrane proteins, thereby enhancing the efficiency of their identification with regard to the number of identified proteins and unique peptides and the sequence coverage of matched proteins.
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Affiliation(s)
- Yong Lin
- College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, PR China
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13
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A conserved hydrogen-bond network in the catalytic centre of animal glutaminyl cyclases is critical for catalysis. Biochem J 2008; 411:181-90. [DOI: 10.1042/bj20071073] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
QCs (glutaminyl cyclases; glutaminyl-peptide cyclotransferases, EC 2.3.2.5) catalyse N-terminal pyroglutamate formation in numerous bioactive peptides and proteins. The enzymes were reported to be involved in several pathological conditions such as amyloidotic disease, osteoporosis, rheumatoid arthritis and melanoma. The crystal structure of human QC revealed an unusual H-bond (hydrogen-bond) network in the active site, formed by several highly conserved residues (Ser160, Glu201, Asp248, Asp305 and His319), within which Glu201 and Asp248 were found to bind to substrate. In the present study we combined steady-state enzyme kinetic and X-ray structural analyses of 11 single-mutation human QCs to investigate the roles of the H-bond network in catalysis. Our results showed that disrupting one or both of the central H-bonds, i.e., Glu201···Asp305 and Asp248···Asp305, reduced the steady-state catalysis dramatically. The roles of these two COOH···COOH bonds on catalysis could be partly replaced by COOH···water bonds, but not by COOH···CONH2 bonds, reminiscent of the low-barrier Asp···Asp H-bond in the active site of pepsin-like aspartic peptidases. Mutations on Asp305, a residue located at the centre of the H-bond network, raised the Km value of the enzyme by 4.4–19-fold, but decreased the kcat value by 79–2842-fold, indicating that Asp305 primarily plays a catalytic role. In addition, results from mutational studies on Ser160 and His319 suggest that these two residues might help to stabilize the conformations of Asp248 and Asp305 respectively. These data allow us to propose an essential proton transfer between Glu201, Asp305 and Asp248 during the catalysis by animal QCs.
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14
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Schilling S, Stenzel I, von Bohlen A, Wermann M, Schulz K, Demuth HU, Wasternack C. Isolation and characterization of the glutaminyl cyclases from Solanum tuberosum and Arabidopsis thaliana: implications for physiological functions. Biol Chem 2007; 388:145-53. [PMID: 17261077 DOI: 10.1515/bc.2007.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Glutaminyl cyclases (QCs) catalyze the formation of pyroglutamic acid at the N-terminus of several peptides and proteins. On the basis of the amino acid sequence of Carica papaya QC, we identified cDNAs of the putative counterparts from Solanum tuberosum and Arabidopsis thaliana. Upon expression of the corresponding cDNAs from both plants via the secretory pathway of Pichia pastoris, two active QC proteins were isolated. The specificity of the purified proteins was assessed using various substrates with different amino acid composition and length. Highest specificities were observed with substrates possessing large hydrophobic residues adjacent to the N-terminal glutamine and for fluorogenic dipeptide surrogates. However, compared to Carica papaya QC, the specificity constants were approximately one order of magnitude lower for most of the QC substrates analyzed. The QCs also catalyzed the conversion of N-terminal glutamic acid to pyroglutamic acid, but with approximately 10(5)- to 10(6)-fold lower specificity. The ubiquitous distribution of plant QCs prompted a search for potential substrates in plants. Based on database entries, numerous proteins, e.g., pathogenesis-related proteins, were found that carry a pyroglutamate residue at the N-terminus, suggesting QC involvement. The putative relevance of QCs and pyroglutamic acid for plant defense reactions is discussed.
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Kyndt T, Van Damme EJM, Van Beeumen J, Gheysen G. Purification and characterization of the cysteine proteinases in the latex of Vasconcellea spp. FEBS J 2006; 274:451-62. [PMID: 17229150 DOI: 10.1111/j.1742-4658.2006.05592.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Latex of all Vasconcellea species analyzed to date exhibits higher proteolytic amidase activities, generally attributed to cysteine proteinases, than the latex of Carica papaya. In the present study, we show that this higher activity is correlated with a higher concentration of enzymes in the latex of Vasconcellea fruits, but in addition also results from the presence of other cysteine proteinases or isoforms. In contrast to the cysteine proteinases present in papaya latex, which have been extensively studied, very little is known about the cysteine proteinases of Vasconcellea spp. In this investigation, several cDNA sequences coding for cysteine proteinases in Vasconcellea x heilbornii and Vasconcellea stipulata were determined using primers based on conserved sequences. In silico translation showed that they hold the characteristic features of all known papain-class cysteine proteinases, and a phylogenetic analysis revealed the existence of several papain and chymopapain homologues in these species. Ion-exchange chromatography and gel filtration procedures were applied on latex of V. x heilbornii in order to characterize its cysteine proteinases at the protein level. Five major protein fractions (VXH-I-VXH-V) revealing very high amidase activities (between 7.5 and 23.3 nkat x mg protein(-1)) were isolated. After further purification, three of them were N-terminally sequenced. The observed microheterogeneity in the N-terminal and cDNA sequences reveals the presence of several distinct cysteine proteinase isoforms in the latex of Vasconcellea spp.
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Affiliation(s)
- Tina Kyndt
- Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Belgium
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Pawlak J, Manjunatha Kini R. Snake venom glutaminyl cyclase. Toxicon 2006; 48:278-86. [PMID: 16863655 DOI: 10.1016/j.toxicon.2006.05.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2006] [Revised: 05/24/2006] [Accepted: 05/30/2006] [Indexed: 10/24/2022]
Abstract
Glutaminyl cyclase (QC) catalyzes N-terminal glutamine cyclization of many endocrine peptides and is typically abundant in brain tissue. As three-finger toxins in the venoms of colubrid snakes Boiga dendrophila and Boiga irregularis contain N-terminal pyroglutamate, we searched for QC in venom glands of both snakes. Here we report cDNA sequences of QC from brain and venom gland tissues of Boiga species. We propose that QC expressed in snake venom gland tissue plays a role in the N-terminal pyroglutamate formation of several snake venom toxins, indirectly contributing to venom potency.
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Affiliation(s)
- Joanna Pawlak
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Science Drive 4, Singapore 117543, Singapore
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Azarkan M, Dibiani R, Goormaghtigh E, Raussens V, Baeyens-Volant D. The papaya Kunitz-type trypsin inhibitor is a highly stable beta-sheet glycoprotein. BIOCHIMICA ET BIOPHYSICA ACTA 2006; 1764:1063-72. [PMID: 16731056 DOI: 10.1016/j.bbapap.2006.02.014] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 01/27/2006] [Accepted: 02/03/2006] [Indexed: 11/16/2022]
Abstract
The papaya Kunitz-type trypsin inhibitor, a 24-kDa glycoprotein, was purified to homogeneity. The purified inhibitor stoichiometrically inhibits bovine trypsin in a 1:1 molar ratio. Circular dichroism and infrared spectroscopy analyses demonstrated that the inhibitor contains extensive beta-sheet structures. The inhibitor was found to retain its full inhibitory activity over a broad pH range (1.5-11.0) and temperature (up to 80 degrees C), besides being stable at very high concentrations of strong chemical denaturants (e.g., 5.5 M guanidine hydrochloride). The inhibitor retained its compact structure over the pH range analyzed as shown by 8-anilino-1-naphtalenesulfonic acid binding characteristics, excluding the formation of some relaxed or molten state. Exposure to 2.5 mM dithiothreitol for 120 min caused a 33% loss of the inhibitory activity, while a loss of 75% was obtained in the presence of 20 mM of dithiothreitol during the same time period. A complete loss of the inhibitory activity was observed after incubation with 50 mM dithiothreitol for 5 min. Incubation of the inhibitor with general proteases belonging to different families revealed its extraordinary resistance to proteolysis in comparison with the soybean trypsin inhibitor, the archetypal member of the Kunitz-type inhibitors family. The inhibitor also exhibited a remarkable resistance to proteolytic degradation against pepsin for at least a 24-h incubation period. Instead, the soybean inhibitor was completely degraded after 2 h incubation with this aspartic protease. All these data demonstrated the high stability of the papaya trypsin inhibitor.
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Affiliation(s)
- Mohamed Azarkan
- University of Brussels, Faculty of Medicine, Protein Chemistry Unit, Campus Erasme (CP 609), 808, route de Lennik, Bz-1070 Brussels, Belgium
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Azarkan M, Dibiani R, Baulard C, Baeyens-Volant D. Effects of mechanical wounding on Carica papaya cysteine endopeptidases accumulation and activity. Int J Biol Macromol 2006; 38:216-24. [PMID: 16580724 DOI: 10.1016/j.ijbiomac.2006.02.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 02/17/2006] [Accepted: 02/17/2006] [Indexed: 11/29/2022]
Abstract
The mechanical wounding impact on the Carica papaya latex protein pattern was investigated by analyzing three latexes. A first one commercially available, a second harvested from unripe but fully grown fruits, both obtained from regularly tapped fruits. A third one was collected from similar fruits but wounded for the first time. The results demonstrated both quantitative and qualitative changes in the protein content and in the enzymatic activity. Repeated wounding results in either, accumulation or activation (or both of them) of papain, chymopapain and caricain. Furthermore, new cysteine protease activity was found to transiently accumulate in the latex collected from newly wounded fruits. The possible implication of this enzymatic material in the papaya cysteine endopeptidases pro-forms activation is discussed.
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Affiliation(s)
- Mohamed Azarkan
- University of Brussels, Faculty of Medicine, Protein Chemistry Unit, Campus Erasme CP 609, 808, route de Lennik, B-1070 Brussels, Belgium.
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Wintjens R, Belrhali H, Clantin B, Azarkan M, Bompard C, Baeyens-Volant D, Looze Y, Villeret V. Crystal Structure of Papaya Glutaminyl Cyclase, an Archetype for Plant and Bacterial Glutaminyl Cyclases. J Mol Biol 2006; 357:457-70. [PMID: 16438985 DOI: 10.1016/j.jmb.2005.12.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 12/08/2005] [Accepted: 12/09/2005] [Indexed: 10/25/2022]
Abstract
Glutaminyl cyclases (QCs) (EC 2.3.2.5) catalyze the intramolecular cyclization of protein N-terminal glutamine residues into pyroglutamic acid with the concomitant liberation of ammonia. QCs may be classified in two groups containing, respectively, the mammalian enzymes, and the enzymes from plants, bacteria, and parasites. The crystal structure of the QC from the latex of Carica papaya (PQC) has been determined at 1.7A resolution. The structure was solved by the single wavelength anomalous diffraction technique using sulfur and zinc as anomalous scatterers. The enzyme folds into a five-bladed beta-propeller, with two additional alpha-helices and one beta hairpin. The propeller closure is achieved via an original molecular velcro, which links the last two blades into a large eight stranded beta-sheet. The zinc ion present in the PQC is bound via an octahedral coordination into an elongated cavity located along the pseudo 5-fold axis of the beta-propeller fold. This zinc ion presumably plays a structural role and may contribute to the exceptional stability of PQC, along with an extended hydrophobic packing, the absence of long loops, the three-joint molecular velcro and the overall folding itself. Multiple sequence alignments combined with structural analyses have allowed us to tentatively locate the active site, which is filled in the crystal structure either by a Tris molecule or an acetate ion. These analyses are further supported by the experimental evidence that Tris is a competitive inhibitor of PQC. The active site is located at the C-terminal entrance of the PQC central tunnel. W83, W110, W169, Q24, E69, N155, K225, F22 and F67 are highly conserved residues in the C-terminal entrance, and their putative role in catalysis is discussed. The PQC structure is representative of the plants, bacterial and parasite enzymes and contrasts with that of mammalian enzymes, that may possibly share a conserved scaffold of the bacterial aminopeptidase.
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Affiliation(s)
- René Wintjens
- Laboratoire de Chimie Générale, Institut de Pharmacie-U.L.B. CP 206/04, Boulevard du Triomphe, B-1050 Brussels, Belgium
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Naqvi SMS, Harper A, Carter C, Ren G, Guirgis A, York WS, Thornburg RW. Nectarin IV, a potent endoglucanase inhibitor secreted into the nectar of ornamental tobacco plants. Isolation, cloning, and characterization. PLANT PHYSIOLOGY 2005; 139:1389-400. [PMID: 16244157 PMCID: PMC1283774 DOI: 10.1104/pp.105.065227] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 08/15/2005] [Accepted: 09/12/2005] [Indexed: 05/05/2023]
Abstract
We have isolated and characterized the Nectarin IV (NEC4) protein that accumulates in the nectar of ornamental tobacco plants (Nicotiana langsdorffii x Nicotiana sanderae var LxS8). This 60-kD protein has a blocked N terminus. Three tryptic peptides of the protein were isolated and sequenced using tandem mass spectroscopy. These unique peptides were found to be similar to the xyloglucan-specific fungal endoglucanase inhibitor protein (XEGIP) precursor in tomato (Lycopersicon esculentum) and its homolog in potato (Solanum tuberosum). A pair of oligonucleotide primers was designed based on the potato and tomato sequences that were used to clone a 1,018-bp internal piece of nec4 cDNA from a stage 6 nectary cDNA library. The remaining portions of the cDNA were subsequently captured by 5' and 3' rapid amplification of cDNA ends. Complete sequencing of the nec4 cDNA demonstrated that it belonged to a large family of homologous proteins from a wide variety of angiosperms. Related proteins include foliage proteins and seed storage proteins. Based upon conserved identity with the wheat (Triticum aestivum) xylanase inhibitor TAXI-1, we were able to develop a protein model that showed that NEC4 contains additional amino acid loops that are not found in TAXI-1 and that glycosylation sites are surface exposed. Both these loops and sites of glycosylation are on the opposite face of the NEC4 molecule from the site that interacts with fungal hemicellulases, as indicated by homology to TAXI-I. NEC4 also contains a region homologous to the TAXI-1 knottin domain; however, a deletion in this domain restructures the disulfide bridges of this domain, resulting in a pseudoknottin domain. Inhibition assays were performed to determine whether purified NEC4 was able to inhibit fungal endoglucanases and xylanases. These studies showed that NEC4 was a very effective inhibitor of a family GH12 xyloglucan-specific endoglucanase with a K(i) of 0.35 nm. However, no inhibitory activity was observed against other family GH10 or GH11 xylanases. The patterns of expression of the NEC4 protein indicate that, while expressed in nectar at anthesis, it is most strongly expressed in the nectary gland after fertilization, indicating that inhibition of fungal cell wall-degrading enzymes may be more important after fertilization than before.
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Affiliation(s)
- S M Saqlan Naqvi
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IW 50011, USA
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21
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Huang KF, Liu YL, Cheng WJ, Ko TP, Wang AHJ. Crystal structures of human glutaminyl cyclase, an enzyme responsible for protein N-terminal pyroglutamate formation. Proc Natl Acad Sci U S A 2005; 102:13117-22. [PMID: 16135565 PMCID: PMC1201592 DOI: 10.1073/pnas.0504184102] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Indexed: 11/18/2022] Open
Abstract
N-terminal pyroglutamate (pGlu) formation from its glutaminyl (or glutamyl) precursor is required in the maturation of numerous bioactive peptides. The aberrant formation of pGlu may be related to several pathological processes, such as osteoporosis and amyloidotic diseases. This N-terminal cyclization reaction, once thought to proceed spontaneously, is greatly facilitated by the enzyme glutaminyl cyclase (QC). To probe this important but poorly understood modification, we present here the structure of human QC in free form and bound to a substrate and three imidazole-derived inhibitors. The structure reveals an alpha/beta scaffold akin to that of two-zinc exopeptidases but with several insertions and deletions, particularly in the active-site region. The relatively closed active site displays alternate conformations due to the different indole orientations of Trp-207, resulting in two substrate (glutamine t-butyl ester)-binding modes. The single zinc ion in the active site is coordinated to three conserved residues and one water molecule, which is replaced by an imidazole nitrogen upon binding of the inhibitors. Together with structural and kinetic analyses of several active-site-mutant enzymes, a catalysis mechanism of the formation of protein N-terminal pGlu is proposed. Our results provide a structural basis for the rational design of inhibitors against QC-associated disorders.
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Affiliation(s)
- Kai-Fa Huang
- Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan
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22
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Huang KF, Liu YL, Wang AHJ. Cloning, expression, characterization, and crystallization of a glutaminyl cyclase from human bone marrow: A single zinc metalloenzyme. Protein Expr Purif 2005; 43:65-72. [PMID: 16084398 DOI: 10.1016/j.pep.2005.02.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 02/22/2005] [Accepted: 02/22/2005] [Indexed: 11/19/2022]
Abstract
Glutaminyl cyclase (QC) catalyzes the N-terminal pyroglutamate formation of numerous hormones and peptides from their glutaminyl precursor. Pyroglutamate is a posttranslational or cotranslational modification important in many physiological and pathological processes. Here, we present the cloning of a QC cDNA from human bone marrow cDNA library. The protein was expressed in Escherichia coli system with the yields higher than approximately 10 mg/L bacterial culture, using a thioredoxin-tagged expression vector with several modifications. Based on high histidine content ( approximately 5%) of the protein, a convenient purification step by Ni-affinity chromatography was designed, leading to near homogeneity of the purified human QC. The identity of the recombinant human QC was confirmed by mass spectrometry and circular dichroism spectroscopy. The enzyme was active on both synthetic and physiological substrates, and the activity could be inhibited by several imidazole, triazole, and tetrazole derivatives. An atomic absorption analysis demonstrated that human QC contains one zinc ion per protein molecule. We also obtained the human QC crystals, which belong to cubic, tetragonal, and rhombohedral forms. Our works are useful to acquire new insights into human and animal QCs, particularly for future structural analysis and inhibitor designs.
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Affiliation(s)
- Kai-Fa Huang
- Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan
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23
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Azarkan M, Clantin B, Bompard C, Belrhali H, Baeyens-Volant D, Looze Y, Villeret V, Wintjens R. Crystallization and preliminary X-ray diffraction studies of the glutaminyl cyclase from Carica papaya latex. Acta Crystallogr Sect F Struct Biol Cryst Commun 2004; 61:59-61. [PMID: 16508091 PMCID: PMC1952388 DOI: 10.1107/s1744309104025904] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Accepted: 10/13/2004] [Indexed: 11/10/2022]
Abstract
In living systems, the intramolecular cyclization of N-terminal glutamine residues is accomplished by glutaminyl cyclase enzymes (EC 2.3.2.5). While in mammals these enzymes are involved in the synthesis of hormonal and neurotransmitter peptides, the physiological role played by the corresponding plant enzymes still remains to be unravelled. Papaya glutaminyl cyclase (PQC), a 33 kDa enzyme found in the latex of the tropical tree Carica papaya, displays an exceptional resistance to chemical and thermal denaturation as well as to proteolysis. In order to elucidate its enzymatic mechanism and to gain insights into the structural determinants underlying its remarkable stability, PQC was isolated from papaya latex, purified and crystallized by the hanging-drop vapour-diffusion method. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 62.82, b = 81.23, c = 108.17 A and two molecules per asymmetric unit. Diffraction data have been collected at ESRF beamline BM14 and processed to a resolution of 1.7 A.
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Affiliation(s)
- Mohamed Azarkan
- Laboratoire de Chimie Générale I, Faculté de Médecine–ULB CP609, 808 Route de Lennik, B-1070 Brussels, Belgium
| | - Bernard Clantin
- CNRS–UMR 8525, Institut de Biologie de Lille, BP 477, 1 Rue du Professeur Calmette, F-59021 Lille, France
| | - Coralie Bompard
- CNRS–UMR 8525, Institut de Biologie de Lille, BP 477, 1 Rue du Professeur Calmette, F-59021 Lille, France
| | - Hassan Belrhali
- EMBL Grenoble Outstation, 6 Rue Jules Horowitz, BP 181, F-38042 Grenoble CEDEX 9, France
| | - Danielle Baeyens-Volant
- Laboratoire de Chimie Générale I, Faculté de Médecine–ULB CP609, 808 Route de Lennik, B-1070 Brussels, Belgium
| | - Yvan Looze
- Laboratoire de Chimie Générale, Institut de Pharmacie–ULB CP206/04, Boulevard du Triomphe, B-1050 Brussels, Belgium
| | - Vincent Villeret
- CNRS–UMR 8525, Institut de Biologie de Lille, BP 477, 1 Rue du Professeur Calmette, F-59021 Lille, France
- Correspondence e-mail: ,
| | - René Wintjens
- Laboratoire de Chimie Générale, Institut de Pharmacie–ULB CP206/04, Boulevard du Triomphe, B-1050 Brussels, Belgium
- Correspondence e-mail: ,
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Schilling S, Manhart S, Hoffmann T, Ludwig HH, Wasternack C, Demuth HU. Substrate specificity of glutaminyl cyclases from plants and animals. Biol Chem 2004; 384:1583-92. [PMID: 14719800 DOI: 10.1515/bc.2003.175] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Glutaminyl cyclases (QC) catalyze the intramolecular cyclization of N-terminal glutamine residues of peptides and proteins. For a comparison of the substrate specificity of human and papaya QC enzymes, a novel continuous assay was established by adapting an existing discontinuous method. Specificity constants (kcat/Km) of dipeptides and dipeptide surrogates were higher for plant QC, whereas the selectivity for oligopeptides was similar for both enzymes. However, only the specificity constants of mammalian QC were dependent on size and composition of the substrates. Specificity constants of both enzymes were equally pH-dependent in the acidic pH-region, revealing a pKa value identical to the pKa of the substrate, suggesting similarities in the substrate conversion mode. Accordingly, both QCs converted the L-beta homoglutaminyl residue in the peptide H-beta homoGln-Phe-Lys-Arg-Leu-Ala-NH2 and the glutaminyl residues of the branched peptide H-Gln-Lys(Gln)-Arg-Leu-Ala-NH2 as well as the partially cyclized peptide H-Gln-cyclo(N epsilon-Lys-Arg-Pro-Ala-Gly-Phe). In contrast, only QC from C. papaya was able to cyclize a methylated glutamine residue, while this compound did not even inhibit human QC-catalysis, suggesting distinct substrate recognition pattern. The conversion of the potential physiological substrates [Gln1]-gastrin, [Gln1]-neurotensin and [Gln1]-fertilization promoting peptide indicates that human QC may play a key role in posttranslational modification of most if not all pGlu-containing hormones.
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25
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Human glutaminyl cyclase and bacterial zinc aminopeptidase share a common fold and active site. BMC Biol 2004; 2:2. [PMID: 15028118 PMCID: PMC368447 DOI: 10.1186/1741-7007-2-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Accepted: 02/10/2004] [Indexed: 11/16/2022] Open
Abstract
Background Glutaminyl cyclase (QC) forms the pyroglutamyl residue at the amino terminus of numerous secretory peptides and proteins. We previously proposed the mammalian QC has some features in common with zinc aminopeptidases. We now have generated a structural model for human QC based on the aminopeptidase fold (pdb code 1AMP) and mutated the apparent active site residues to assess their role in QC catalysis. Results The structural model proposed here for human QC, deposited in the protein databank as 1MOI, is supported by a variety of fold prediction programs, by the circular dichroism spectrum, and by the presence of the disulfide. Mutagenesis of the six active site residues present in both 1AMP and QC reveal essential roles for the two histidines (140 and 330, QC numbering) and the two glutamates (201 and 202), while the two aspartates (159 and 248) appear to play no catalytic role. ICP-MS analysis shows less than stoichiometric zinc (0.3:1) in the purified enzyme. Conclusions We conclude that human pituitary glutaminyl cyclase and bacterial zinc aminopeptidase share a common fold and active site residues. In contrast to the aminopeptidase, however, QC does not appear to require zinc for enzymatic activity.
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26
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Schilling S, Niestroj AJ, Rahfeld JU, Hoffmann T, Wermann M, Zunkel K, Wasternack C, Demuth HU. Identification of Human Glutaminyl Cyclase as a Metalloenzyme. J Biol Chem 2003; 278:49773-9. [PMID: 14522962 DOI: 10.1074/jbc.m309077200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human glutaminyl cyclase (QC) was identified as a metalloenzyme as suggested by the time-dependent inhibition by the heterocyclic chelators 1,10-phenanthroline and dipicolinic acid. The effect of EDTA on QC catalysis was negligible. Inactivated enzyme could be fully restored by the addition of Zn2+ in the presence of equimolar concentrations of EDTA. Little reactivation was observed with Co2+ and Mn2+. Other metal ions such as K+, Ca2+, and Ni2+ were inactive under the same conditions. Additionally, imidazole and imidazole derivatives were identified as competitive inhibitors of QC. An initial structure activity-based inhibitor screening of imidazole-derived compounds revealed potent inhibition of QC by imidazole N-1 derivatives. Subsequent data base screening led to the identification of two highly potent inhibitors, 3-[3-(1H-imidazol-1-yl)propyl]-2-thioxoimidazolidin-4-one and 1,4-bis-(imidazol-1-yl)-methyl-2,5-dimethylbenzene, which exhibited respective Ki values of 818 +/- 1 and 295 +/- 5 nm. The binding properties of the imidazole derivatives were further analyzed by the pH dependence of QC inhibition. The kinetically obtained pKa values of 6.94 +/- 0.02, 6.93 +/- 0.03, and 5.60 +/- 0.05 for imidazole, methylimidazole, and benzimidazole, respectively, match the values obtained by titrimetric pKa determination, indicating the requirement for an unprotonated nitrogen for binding to QC. Similarly, the pH dependence of the kinetic parameter Km for the QC-catalyzed conversion of H-Gln-7-ami-no-4-methylcoumarin also implies that only N-terminally unprotonated substrate molecules are bound to the active site of the enzyme, whereas turnover is not affected. The results reveal human QC as a metal-dependent transferase, suggesting that the active site-bound metal is a potential site for interaction with novel, highly potent competitive inhibitors.
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27
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Azarkan M, El Moussaoui A, van Wuytswinkel D, Dehon G, Looze Y. Fractionation and purification of the enzymes stored in the latex of Carica papaya. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 790:229-38. [PMID: 12767335 DOI: 10.1016/s1570-0232(03)00084-9] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The latex of the tropical species Carica papaya is well known for being a rich source of the four cysteine endopeptidases papain, chymopapain, glycyl endopeptidase and caricain. Altogether, these enzymes are present in the laticifers at a concentration higher than 1 mM. The proteinases are synthesized as inactive precursors that convert into mature enzymes within 2 min after wounding the plant when the latex is abruptly expelled. Papaya latex also contains other enzymes as minor constituents. Several of these enzymes namely a class-II and a class-III chitinase, an inhibitor of serine proteinases and a glutaminyl cyclotransferase have already been purified up to apparent homogeneity and characterized. The presence of a beta-1,3-glucanase and of a cystatin is also suspected but they have not yet been isolated. Purification of these papaya enzymes calls on the use of ion-exchange supports (such as SP-Sepharose Fast Flow) and hydrophobic supports [such as Fractogel TSK Butyl 650(M), Fractogel EMD Propyl 650(S) or Thiophilic gels]. The use of covalent or affinity gels is recommended to provide preparations of cysteine endopeptidases with a high free thiol content (ideally 1 mol of essential free thiol function per mol of enzyme). The selective grafting of activated methoxypoly(ethylene glycol) chains (with M(r) of 5000) on the free thiol functions of the proteinases provides an interesting alternative to the use of covalent and affinity chromatographies especially in the case of enzymes such as chymopapain that contains, in its native state, two thiol functions.
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Affiliation(s)
- Mohamed Azarkan
- Laboratoire de Chimie Générale, Unité de Chimie des Protéines (CP 609), Faculté de Médecine, Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, B-1070, Brussels, Belgium
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28
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Morrow JA, Hatters DM, Lu B, Hochtl P, Oberg KA, Rupp B, Weisgraber KH. Apolipoprotein E4 forms a molten globule. A potential basis for its association with disease. J Biol Chem 2002; 277:50380-5. [PMID: 12393895 DOI: 10.1074/jbc.m204898200] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The amino-terminal domain of apolipoprotein (apo) E4 is less susceptible to chemical and thermal denaturation than the apoE3 and apoE2 domains. We compared the urea denaturation curves of the 22-kDa amino-terminal domains of the apoE isoforms at pH 7.4 and 4.0. At pH 7.4, apoE3 and apoE4 reflected an apparent two-state denaturation. The midpoints of denaturation were 5.2 and 4.3 m urea, respectively. At pH 4.0, a pH value known to stabilize folding intermediates, apoE4 and apoE3 displayed the same order of denaturation but with distinct plateaus, suggesting the presence of a stable folding intermediate. In contrast, apoE2 proved the most stable and lacked the distinct plateau observed with the other two isoforms and could be fitted to a two-state unfolding model. Analysis of the curves with a three-state unfolding model (native, intermediate, and unfolded) showed that the apoE4 folding intermediate reached its maximal concentration ( approximately 90% of the mixture) at 3.75 m, whereas the apoE3 intermediate was maximal at 4.75 m ( approximately 80%). These results are consistent with apoE4 being more susceptible to unfolding than apoE3 and apoE2 and more prone to form a stable folding intermediate. The structure of the apoE4 folding intermediate at pH 4.0 in 3.75 m urea was characterized using pepsin proteolysis, Fourier transform infrared spectroscopy, and dynamic light scattering. From these studies, we conclude that the apoE4 folding intermediate is a single molecule with the characteristics of a molten globule. We propose a model of the apoE4 molten globule in which the four-helix bundle of the amino-terminal domain is partially opened, generating a slightly elongated structure and exposing the hydrophobic core. Since molten globules have been implicated in both normal and abnormal physiological function, the differential abilities of the apoE isoforms to form a molten globule may contribute to the isoform-specific effects of apoE in disease.
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Affiliation(s)
- Julie A Morrow
- Gladstone Institutes of Cardiovascular Disease and Neurological Disease, San Francisco, California 94141-9100, USA
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29
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Azarkan M, Amrani A, Zerhouni S, Oberg KA, Ruysschaert JM, Wintjens R, Looze Y. Evidence that thermodynamic stability of papaya glutamine cyclase is only marginal. Biopolymers 2002; 65:325-35. [PMID: 12389212 DOI: 10.1002/bip.10234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Papaya glutamine cyclase (PQC), a glycoprotein with a molecular mass of 32,980 Da, is a minor constituent of the papaya latex protein fraction. In neutral aqueous solutions, PQC adopts an all-beta conformation and exhibits high resistance to both proteolysis and denaturation. Complete unfolding of PQC requires a combination of an acidic medium and chemical denaturant such as urea or guanidine hydrochloride. The unfolding process takes place through formation of an intermediate A state that accumulates in the absence of chemical denaturants and displays all the features of a molten globule state. The different conformational states-N (native), A (acid-inactivated), and U (unfolded)-have been characterized by means of circular dichroism measurements, fluorescence spectroscopies, Stokes radii determinations, and 8-anilino-1-naphtalenesulfonic acid (ANS) binding characteristics. The unfolding pathways of the enzyme was further studied to estimate thermodynamic parameters characterizing both transitions N if A and A if U. In its A state, PQC is catalytically inefficient and highly susceptible to proteolysis. Also, its thermodynamic stability is decreased by some 3-5 kcal/mol. Conversion of the native to the A state involves digging up of five amino functions together with protonation of four to five acidic groups with pK(a)s, in the native state, around 2.7. It proceeds both cooperatively and reversibly although, in vitro, the refolding process is slow. Unfolding of the A state, on the other hand, occurs with a low degree of cooperativity. The intermediate A state thus seems to be only marginally more stable than the unfolded state. The role of suspected internal ion pairs in the stabilization of the native state of this enzyme is discussed.
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Affiliation(s)
- Mohamed Azarkan
- Protein Chemistry Department (CP 609), Faculty of Medicine, Free University of Brussels, Campus Erasme, 808 Route de Lennik, Belgium
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Schilling S, Hoffmann T, Rosche F, Manhart S, Wasternack C, Demuth HU. Heterologous expression and characterization of human glutaminyl cyclase: evidence for a disulfide bond with importance for catalytic activity. Biochemistry 2002; 41:10849-57. [PMID: 12196024 DOI: 10.1021/bi0260381] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glutaminyl cyclase (QC, EC 2.3.2.5) catalyzes the formation of pyroglutamate residues from glutamine at the N-terminus of peptides and proteins. In the current study, human QC was functionally expressed in the secretory pathway of Pichia pastoris, yielding milligram quantities after purification from the supernatant of a 5 L fermentation. Initial characterization studies of the recombinant QC using MALDI-TOF mass spectrometry revealed correct proteolytic processing and N-glycosylation at both potential sites with similar 2 kDa extensions. CD spectral analysis indicated a high alpha-helical content, which contrasts with plant QC from Carica papaya. The kinetic parameters for conversion of H-Gln-Tyr-Ala-OH by recombinant human QC were almost identical to those previously reported for purified bovine pituitary QC. However, the results obtained for conversion of H-Gln-Gln-OH, H-Gln-NH2, and H-Gln-AMC were found to be contradictory to previous studies on human QC expressed intracellularly in E. coli. Expression of QC in E. coli showed that approximately 50% of the protein did not contain a disulfide bond that is present in the entire QC expressed in P. pastoris. Further, the enzyme was consistently inactivated by treatment with 15 mM DTT, whereas deglycosylation had no effect on enzymatic activity. Analysis of the fluorescence spectra of the native, reduced, and unfolded human QC point to a conformational change of the protein upon treatment with DTT. In terms of the different enzymatic properties, the consequences of QC expression in different environments are discussed.
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Affiliation(s)
- Stephan Schilling
- Laboratory of Biochemistry, Probiodrug AG, Weinbergweg 22, 06120 Halle/Saale, Germany
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31
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Vassilenko KS, Uversky VN. Native-like secondary structure of molten globules. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1594:168-77. [PMID: 11825619 DOI: 10.1016/s0167-4838(01)00303-x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The most common evidence for the existence of secondary structure in a globular protein is the presence of a strongly pronounced far-UV circular dichroism (CD) spectrum. Although CD spectra of native proteins are well described and their quantitative analysis is widely used, similar studies for denatured proteins have still to be done. Far-UV CD spectra of nine proteins in the native and the pH-induced molten globule states were acquired and analyzed. Singular value decomposition showed that the spectra of molten globules could be described as a superposition of at least three independent components (most likely alpha-, beta- and irregular structure). A self-consistent procedure of CD spectra analysis revealed the existence of a clear correlation between the shape of the molten globule spectra and the content of secondary structure elements in the corresponding native proteins, as determined from X-ray data. A mathematical expression of this correlation in terms of the Pierson coefficient amounts to the value of 0.9 for both the alpha-helix and the beta-structure. Thus, the secondary structure of proteins in the molten globule state is close to that in the native state.
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Affiliation(s)
- Konstantin S Vassilenko
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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32
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Permyakov SE, Oberg KA, Cherskaya AM, Shavlovsky MM, Permyakov EA, Uversky VN. Human alpha-fetoprotein as a Zn(2+)-binding protein. Tight cation binding is not accompanied by global changes in protein structure and stability. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1586:1-10. [PMID: 11781144 DOI: 10.1016/s0925-4439(01)00079-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The binding of zinc to human alpha-fetoprotein (AFP) isolated from human umbilical cord serum was studied by fluorimetric Zn(2+)-titration. We found that the total number of strong binding sites for zinc on this protein was 5: AFP has one very strong (dissociation constant, K(d)<10(-8) M) and at least four lower affinity zinc binding sites (K(d)<10(-5) M). Fourier transform infrared (FTIR) analysis revealed that aspartate and histidine residues could be involved in the strong coordination of zinc. Intriguingly, binding of zinc to the protein does not induce structural changes that can be detected by circular dichroism, FTIR, intrinsic fluorescence or (1,1')-bi-(4-anilino)naphthalene-5,5'-disulfonic acid (bis-ANS) binding. Finally, scanning microcalorimetry measurements showed that stability of the protein is also unaffected by zinc binding in spite of the strength of the coordination. Such strong interactions without major structural consequences are highly unusual, and AFP may therefore be the first characterized representative of a new class of ligand-binding proteins.
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Affiliation(s)
- Serge E Permyakov
- Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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Kosarikov DN, Lee JM, Uversky VN, Counts Gerber N. Role of conformational changes in the heme-dependent regulation of human soluble guanylate cyclase. J Inorg Biochem 2001; 87:267-76. [PMID: 11744065 DOI: 10.1016/s0162-0134(01)00387-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Soluble guanylate cyclase (sGC) is a receptor for endogenous and exogenous nitric oxide (NO) and is activated many fold upon its binding, making it a core enzyme in the nitric oxide signal transduction pathway. Much effort has been made to understand the link between binding of NO at the sGC heme and activation of the cyclase activity. We report here the first direct evidence for the role of conformational changes in transmitting the signal between the heme and cyclase domains. Using both circular dichroism (CD) and fluorescence spectroscopies, we have probed the effect that the sGC activators NO and 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl-indazole (YC-1) and the inhibitor 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one (ODQ) have on the structure of the protein. Surprisingly, binding of either ODQ or YC-1 to NO-bound sGC cause virtually identical changes in the far-UV CD spectra of sGC, reflecting a perturbation in the secondary structure of the enzyme. This change is absent upon binding of NO, YC-1 or ODQ alone. Using this and previous data, we propose a working model for the mechanism of activation of sGC by NO and YC-1 and inhibition by ODQ.
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Affiliation(s)
- D N Kosarikov
- Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132-4163, USA
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Bateman RC, Temple JS, Misquitta SA, Booth RE. Evidence for essential histidines in human pituitary glutaminyl cyclase. Biochemistry 2001; 40:11246-50. [PMID: 11551224 DOI: 10.1021/bi011177o] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glutaminyl cyclase (QC, EC 2.3.2.5) catalyzes the formation of the pyroglutamyl residue present at the amino terminus of numerous secretory peptides and proteins. Treatment with diethyl pyrocarbonate inactivated recombinant human QC with the apparent modification of three essential histidine residues. Comparisons of the protein sequences of QC from a variety of eukaryotic species show four completely conserved histidine residues. Mutation of each of these residues to glutamine resulted in two mutant enzymes that were inactive (H140Q and H330Q), suggesting a role in catalysis, and two that exhibited increased Km values (H307Q and H319Q), suggesting a role in substrate binding. Consistent with these results is the prediction that QC possesses a zinc aminopeptidase domain in which the four histidines identified here are present in the active site. Mammalian glutaminyl cyclases may, therefore, have structural and catalytic similarities to a family of bacterial zinc aminopeptidases.
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Affiliation(s)
- R C Bateman
- Department of Chemistry and Biochemistry, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-5043, USA.
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Kosarikov DN, Young P, Uversky VN, Gerber NC. Human Soluble Guanylate Cyclase: Functional Expression, Purification and Structural Characterization. Arch Biochem Biophys 2001; 388:185-97. [PMID: 11368154 DOI: 10.1006/abbi.2001.2284] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Soluble guanylate cyclase is an enzyme that catalyzes formation of cGMP from GTP and is a member of the nucleotide cyclase family of enzymes. sGC is a receptor for endogenous and exogenous nitric oxide and is activated several-fold upon its binding, constituting a core enzyme in the nitric oxide signal transduction pathway. cGMP generated by sGC is an important second messenger that regulates activity of several enzymes triggering such important physiologic reactions as vasodilation, smooth muscle relaxation and platelet aggregation. We report here the functional expression of the human isoform of soluble guanylate cyclase in HighFive insect cells using a baculovirus expression system. Highly active recombinant protein was obtained without heme reconstitution or supplementation of the cell growth medium and the level of protein expression was found to be heavily affected by the composition of the growth medium. We have successfully purified highly active sGC (sp act up to 940 nmol/min/mg) from adherent cultures using a three-column, 1-day procedure. The UV-Vis spectrum of the isolated protein shows a Soret band at 431 nm, consistent with a histidine-ligated, 5-coordinate heme as previously reported. Far UV CD spectroscopy, intrinsic tryptophan fluorescence, fluorescence of the hydrophobic dye bis-ANS, size-exclusion chromatography, and small angle X-ray scattering (SAXS) were used to characterize the structural properties of the purified sGC. We used two hierarchical neural network methods to predict the secondary structure of sGC and found it to be consistent with the observed CD spectrum of sGC.
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Affiliation(s)
- D N Kosarikov
- Department of Chemistry and Biochemistry, San Francisco State University, California, USA
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Dahl SW, Slaughter C, Lauritzen C, Bateman RC, Connerton I, Pedersen J. Carica papaya glutamine cyclotransferase belongs to a novel plant enzyme subfamily: cloning and characterization of the recombinant enzyme. Protein Expr Purif 2000; 20:27-36. [PMID: 11035947 DOI: 10.1006/prep.2000.1273] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A full-length cDNA encoding Carica papaya glutamine cyclotransferase was cloned by RT-PCR on the basis of results from amino acid sequencing of tryptic fragments of the native enzyme. The cDNA of 1036 nucleotides encodes a typical 22-residue signal peptide and a mature protein of 266 residues with a calculated molecular mass of 30,923 Da. Five plant ESTs encoding putative QCs highly homologous to PQC were identified and the numbers and locations of cysteines and N-glycosylation sites are conserved. The plant QC amino acid sequences are very different from the known mammalian QC sequences and no clear homology was observed. The PQC cDNA was expressed in Escherichia coli as either His-tagged PQC, with three different signal peptides and in fusions with thioredoxin, glutathione S-transferase, and (pre-) maltose-binding protein. In all cases, the expressed protein was either undetectable or insoluble. Expression in Pichia pastoris of PQC fused to the alpha-factor leader resulted in low levels of PQC activity. Extracellular expression of PQC in the insect cell/baculovirus system was successful and 15-50 mg/liter of active PQCs with three different secretion signals was expressed and purified. Further, PQC N-terminally fused to a combined secretion signal/His-tag peptide was correctly processed by the host signal peptidase and the His-tag could subsequently be removed with dipeptidyl peptidase I. The expressed products were characterized by activity assays, SDS-PAGE, N-terminal amino acid sequencing, MALDI-TOF mass spectroscopy, and peptide mass fingerprint analysis.
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Affiliation(s)
- S W Dahl
- Unizyme Laboratories A/S, Dr. Neergaards Vej 17, Horsholm, Denmark,
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Prévost M, Jacquemotte F, Oberg KA, Staelens D, Devreese B, Van Beeumen J. Conformational variability of the synthetic peptide 129-141 of the mouse prion protein. J Biomol Struct Dyn 2000; 18:237-48. [PMID: 11089645 DOI: 10.1080/07391102.2000.10506662] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The effect of solution conditions on the conformation of the peptide corresponding to residues 129-141 of the mouse prion protein has been examined by experimental and theoretical tools including circular dichroism, secondary structure predictions, and Molecular Dynamics simulations. The conformational properties of the peptide observed by CD confirm the prediction results: the peptide is chiefly random coil in water. The conformational sampling performed by Molecular Dynamics simulations in water also corroborates the flexibility of the peptide, in particular for the N-terminal part. We show, however, that the peptide samples hairpin conformations in one of several approximately 1-ns Molecular Dynamics simulations in water. Interestingly, the analysis of the CD spectra obtained in this study suggests the presence of beta-structure which, given the length of the peptide, can only consist in beta-hairpin. The peptide can also be induced to form a modest percentage of helical structure in the presence of organic cosolvents such as trifluoroethanol, or detergents such as sodium dodecyl sulfate and lysophosphatidylcholine. This result is different from that obtained for a homologous hamster fragment, which differs from the mouse sequence by the single substitution of Ile 139 to Met. Interestingly, this substitution is crucial for the barrier in the transmission of the prion disease between hamsters and mice.
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Affiliation(s)
- M Prévost
- Ingénierie Biomoléculaire, Université Libre de Bruxelles, Belgium.
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Goormaghtigh E, Raussens V, Ruysschaert JM. Attenuated total reflection infrared spectroscopy of proteins and lipids in biological membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1422:105-85. [PMID: 10393271 DOI: 10.1016/s0304-4157(99)00004-0] [Citation(s) in RCA: 452] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- E Goormaghtigh
- Laboratoire de Chimie-Physique des Macromolécules aux Interfaces, P. O. Box 206/2, Université Libre de Bruxelles, Campus Plaine, B-1050, Brussels, Belgium.
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