1
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Rahaman MH, Thygesen SJ, Maxwell MJ, Kim H, Mudai P, Nanson JD, Jia X, Vajjhala PR, Hedger A, Vetter I, Haselhorst T, Robertson AAB, Dymock B, Ve T, Mobli M, Stacey KJ, Kobe B. o-Vanillin binds covalently to MAL/TIRAP Lys-210 but independently inhibits TLR2. J Enzyme Inhib Med Chem 2024; 39:2313055. [PMID: 38416868 PMCID: PMC10903754 DOI: 10.1080/14756366.2024.2313055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 01/28/2024] [Indexed: 03/01/2024] Open
Abstract
Toll-like receptor (TLR) innate immunity signalling protects against pathogens, but excessive or prolonged signalling contributes to a range of inflammatory conditions. Structural information on the TLR cytoplasmic TIR (Toll/interleukin-1 receptor) domains and the downstream adaptor proteins can help us develop inhibitors targeting this pathway. The small molecule o-vanillin has previously been reported as an inhibitor of TLR2 signalling. To study its mechanism of action, we tested its binding to the TIR domain of the TLR adaptor MAL/TIRAP (MALTIR). We show that o-vanillin binds to MALTIR and inhibits its higher-order assembly in vitro. Using NMR approaches, we show that o-vanillin forms a covalent bond with lysine 210 of MAL. We confirm in mouse and human cells that o-vanillin inhibits TLR2 but not TLR4 signalling, independently of MAL, suggesting it may covalently modify TLR2 signalling complexes directly. Reactive aldehyde-containing small molecules such as o-vanillin may target multiple proteins in the cell.
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Affiliation(s)
- Md. Habibur Rahaman
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Sara J. Thygesen
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Michael J. Maxwell
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Hyoyoung Kim
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Prerna Mudai
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Jeffrey D. Nanson
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Xinying Jia
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Parimala R. Vajjhala
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
| | - Andrew Hedger
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
- School of Pharmacy, University of Queensland, Brisbane, Australia
| | | | - Avril A. B. Robertson
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Brian Dymock
- Queensland Emory Drug Discovery Initiative, University of Queensland, Brisbane, Australia
| | - Thomas Ve
- Institute for Glycomics, Griffith University, Southport, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, University of Queensland, Brisbane, Australia
| | - Katryn J. Stacey
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia
- Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
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2
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Schnetler R, Fanucchi S, Moldoveanu T, Koorsen G. Linker Histone H1.2 Directly Activates BAK through the K/RVVKP Motif on the C-Terminal Domain. Biochemistry 2020; 59:3332-3346. [PMID: 32786407 DOI: 10.1021/acs.biochem.0c00373] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
H1.2 is a key mediator of apoptosis following DNA double-strand breaks. The link between H1.2 and canonical apoptotic pathways is unclear. One study found that H1.2 stimulates cytochrome c (Cyt c) release; in contrast, apoptosis-inducing factor was found to be released in another study. The C-terminal domain (CTD) of H1.2 has been implicated in the latter pathway, but activation of the proapoptotic protein BCL-2 homologous antagonist/killer (BAK) is a common denominator in both pathways. This study aimed to determine whether the CTD of H1.2 is also responsible for mitochondrial Cyt c release and whether a previously identified K/RVVKP motif in the CTD mediates the response. This study investigated if H1.2 mediates apoptosis induction through direct interaction with BAK. We established that the CTD of H1.2 stimulates mitochondrial Cyt c release in vitro in a mitochondrial permeability transition-independent manner and that the substitution of a single valine with threonine in the K/RVVKP motif abolishes Cyt c release. Additionally, we showed that H1.2 directly interacts with BAK with weak affinity and that the CTD of H1.2 mediates this binding. Using two 20-amino acid peptides derived from the CTD of H1.2 and H1.1 (K/RVVKP motif inclusive), we determined the main residues involved in the direct interaction with BAK. We propose that H1.2 operates through the K/RVVKP motif by directly activating BAK through inter- and intramolecular interactions. These findings expand the view of H1.2 as a signal-transducing molecule that can activate apoptosis in a BAK-dependent manner.
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Affiliation(s)
- Rozanné Schnetler
- Department of Biochemistry, University of Johannesburg, Corner Kingsway and University Roads, P.O. Box 524, Auckland Park, Johannesburg 2006, South Africa
| | - Sylvia Fanucchi
- Department of Molecular and Cell Biology, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2000, South Africa
| | - Tudor Moldoveanu
- Department of Structural Biology and Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, United States
| | - Gerrit Koorsen
- Department of Biochemistry, University of Johannesburg, Corner Kingsway and University Roads, P.O. Box 524, Auckland Park, Johannesburg 2006, South Africa
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3
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Abstract
Fourier transform infrared (FTIR) spectroscopy has become one of the major techniques of structural characterization of proteins, peptides, and protein-membrane interactions. While the method does not have the capability of providing the precise, atomic-resolution molecular structure, it is exquisitely sensitive to conformational changes occurring in proteins upon functional transitions or intermolecular interactions. The sensitivity of vibrational frequencies to atomic masses has led to development of "isotope-edited" FTIR spectroscopy, where structural effects in two proteins, one unlabeled and the other labeled with a heavier stable isotope, such as 13C, are resolved simultaneously based on spectral downshift (separation) of the amide I band of the labeled protein. The same isotope effect is used to identify site-specific conformational changes in proteins by site-directed or segmental isotope labeling. Negligible light scattering in the infrared region provides an opportunity to study intermolecular interactions between large protein complexes, interactions of proteins and peptides with lipid vesicles, or protein-nucleic acid interactions without light scattering problems often encountered in ultraviolet spectroscopy. Attenuated total reflection FTIR (ATR-FTIR) is a surface-sensitive version of infrared spectroscopy that has proved useful in studying membrane proteins and lipids, protein-membrane interactions, mechanisms of interfacial enzymes, the structural features of membrane pore forming proteins and peptides, and much more. The purpose of this chapter was to provide a practical guide to analyze protein structure and protein-membrane interactions by FTIR and ATR-FTIR techniques, including procedures of sample preparation, measurements, and data analysis. Basic background information on FTIR spectroscopy, as well as some relatively new developments in structural and functional characterization of proteins and peptides in lipid membranes, is also presented.
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Affiliation(s)
- Suren A Tatulian
- Department of Physics, University of Central Florida, Orlando, FL, USA.
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4
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Adeola HA, Van Wyk JC, Arowolo A, Ngwanya RM, Mkentane K, Khumalo NP. Emerging Diagnostic and Therapeutic Potentials of Human Hair Proteomics. Proteomics Clin Appl 2017; 12. [PMID: 28960873 DOI: 10.1002/prca.201700048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 06/09/2017] [Indexed: 01/22/2023]
Abstract
The use of noninvasive human substrates to interrogate pathophysiological conditions has become essential in the post- Human Genome Project era. Due to its high turnover rate, and its long term capability to incorporate exogenous and endogenous substances from the circulation, hair testing is emerging as a key player in monitoring long term drug compliance, chronic alcohol abuse, forensic toxicology, and biomarker discovery, among other things. Novel high-throughput 'omics based approaches like proteomics have been underutilized globally in comprehending human hair morphology and its evolving use as a diagnostic testing substrate in the era of precision medicine. There is paucity of scientific evidence that evaluates the difference in drug incorporation into hair based on lipid content, and very few studies have addressed hair growth rates, hair forms, and the biological consequences of hair grooming or bleaching. It is apparent that protein-based identification using the human hair proteome would play a major role in understanding these parameters akin to DNA single nucleotide polymorphism profiling, up to single amino acid polymorphism resolution. Hence, this work seeks to identify and discuss the progress made thus far in the field of molecular hair testing using proteomic approaches, and identify ways in which proteomics would improve the field of hair research, considering that the human hair is mostly composed of proteins. Gaps in hair proteomics research are identified and the potential of hair proteomics in establishing a historic medical repository of normal and disease-specific proteome is also discussed.
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Affiliation(s)
- Henry A Adeola
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.,Hair and Skin Research Laboratory, Groote Schuur Hospital, Cape Town, South Africa
| | - Jennifer C Van Wyk
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.,Hair and Skin Research Laboratory, Groote Schuur Hospital, Cape Town, South Africa
| | - Afolake Arowolo
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.,Hair and Skin Research Laboratory, Groote Schuur Hospital, Cape Town, South Africa
| | - Reginald M Ngwanya
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa
| | - Khwezikazi Mkentane
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.,Hair and Skin Research Laboratory, Groote Schuur Hospital, Cape Town, South Africa
| | - Nonhlanhla P Khumalo
- Division of Dermatology, Department of Medicine, Faculty of Health Sciences and Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa.,Hair and Skin Research Laboratory, Groote Schuur Hospital, Cape Town, South Africa
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5
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Extra-mitochondrial prosurvival BCL-2 proteins regulate gene transcription by inhibiting the SUFU tumour suppressor. Nat Cell Biol 2017; 19:1226-1236. [PMID: 28945232 PMCID: PMC5657599 DOI: 10.1038/ncb3616] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 08/17/2017] [Indexed: 02/07/2023]
Abstract
Direct interactions between pro- and anti-apoptotic BCL-2 family members form the basis of cell death decision-making at the outer mitochondrial membrane (OMM). Here we report that three antiapoptotic BCL-2 proteins (MCL-1, BCL-2, and BCL-XL) found untethered from the OMM function as transcriptional regulators of a prosurvival and growth program. Antiapoptotic BCL-2 proteins engage a BCL-2 homology (BH) domain sequence found in Suppressor of Fused (SUFU), a tumor suppressor and antagonist of the GLI DNA binding proteins. BCL-2 proteins directly promote SUFU turnover, inhibit SUFU-GLI interaction, and induce the expression of the GLI target genes BCL-2, MCL-1, and BCL-XL. Antiapoptotic BCL-2 protein/SUFU feedforward signaling promotes cancer cell survival and growth and can be disabled with BH3 mimetics – small molecules that target antiapoptotic BCL-2 proteins. Our findings delineate a chemical strategy for countering drug resistance in GLI-associated tumors and reveal unanticipated functions for BCL-2 proteins as transcriptional regulators.
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6
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Gande SL, Saxena K, Sreeramulu S, Linhard V, Kudlinzki D, Heinzlmeir S, Reichert AJ, Skerra A, Kuster B, Schwalbe H. Expression and Purification of EPHA2 Tyrosine Kinase Domain for Crystallographic and NMR Studies. Chembiochem 2016; 17:2257-2263. [DOI: 10.1002/cbic.201600483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Indexed: 01/12/2023]
Affiliation(s)
- Santosh L. Gande
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
| | - Krishna Saxena
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
| | - Sridhar Sreeramulu
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Verena Linhard
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
| | - Denis Kudlinzki
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
| | - Stephanie Heinzlmeir
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
- Chair of Proteomics and Bioanalytics; Technical University of Munich; Emil-Erlenmeyer-Forum 5 85354 Freising Germany
| | - Andreas J. Reichert
- Chair of Biological Chemistry; Technical University of Munich; Emil-Erlenmeyer-Forum 5 85354 Freising Germany
| | - Arne Skerra
- Chair of Biological Chemistry; Technical University of Munich; Emil-Erlenmeyer-Forum 5 85354 Freising Germany
| | - Bernhard Kuster
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
- Chair of Proteomics and Bioanalytics; Technical University of Munich; Emil-Erlenmeyer-Forum 5 85354 Freising Germany
- Center for integrated Protein Science Munich (CIPSM); Technical University of Munich; Arcisstrasse 21 80333 München Germany
- Bavarian Biomolecular Mass Spectrometry Center; Technical University of Munich; Gregor-Mendel-Strasse 4 85354 Freising Germany
| | - Harald Schwalbe
- Center for Biomolecular Magnetic Resonance (BMRZ); Institute for Organic Chemistry and Chemical Biology; Johann Wolfgang Goethe-Universität; Max-von-Laue-Strasse 7 60438 Frankfurt am Main Germany
- German Cancer Consortium (DKTK); In Neuenheimer Feld 280 69120 Heidelberg Germany
- German Cancer Research Center (DKFZ); In Neuenheimer Feld 280 69120 Heidelberg Germany
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7
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Vajjhala PR, Kaiser S, Smith SJ, Ong QR, Soh SL, Stacey KJ, Hill JM. Identification of multifaceted binding modes for pyrin and ASC pyrin domains gives insights into pyrin inflammasome assembly. J Biol Chem 2014; 289:23504-19. [PMID: 25006247 DOI: 10.1074/jbc.m114.553305] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Inflammasomes are macromolecular complexes that mediate inflammatory and cell death responses to pathogens and cellular stress signals. Dysregulated inflammasome activation is associated with autoinflammatory syndromes and several common diseases. During inflammasome assembly, oligomerized cytosolic pattern recognition receptors recruit procaspase-1 and procaspase-8 via the adaptor protein ASC. Inflammasome assembly is mediated by pyrin domains (PYDs) and caspase recruitment domains, which are protein interaction domains of the death fold superfamily. However, the molecular details of their interactions are poorly understood. We have studied the interaction between ASC and pyrin PYDs that mediates ASC recruitment to the pyrin inflammasome, which is implicated in the pathogenesis of familial Mediterranean fever. We demonstrate that both the ASC and pyrin PYDs have multifaceted binding modes, involving three sites on pyrin PYD and two sites on ASC PYD. Molecular docking of pyrin-ASC PYD complexes showed that pyrin PYD can simultaneously interact with up to three ASC PYDs. Furthermore, ASC PYD can self-associate and interact with pyrin, consistent with previous reports that pyrin promotes ASC clustering to form a proinflammatory complex. Finally, the effects of familial Mediterranean fever-associated mutations, R42W and A89T, on structural and functional properties of pyrin PYD were investigated. The R42W mutation had a significant effect on structure and increased stability. Although the R42W mutant exhibited reduced interaction with ASC, it also bound less to the pyrin B-box domain responsible for autoinhibition and hence may be constitutively active. Our data give new insights into the binding modes of PYDs and inflammasome architecture.
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Affiliation(s)
| | | | - Sarah J Smith
- From the School of Chemistry and Molecular Biosciences and
| | - Qi-Rui Ong
- From the School of Chemistry and Molecular Biosciences and
| | | | | | - Justine M Hill
- From the School of Chemistry and Molecular Biosciences and Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland 4072, Australia
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8
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Mas C, Chen KE, Brereton IM, Martin JL, Hill JM. Backbone resonance assignments of the monomeric DUF59 domain of human Fam96a. BIOMOLECULAR NMR ASSIGNMENTS 2013; 7:117-120. [PMID: 22618863 DOI: 10.1007/s12104-012-9390-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 05/03/2012] [Indexed: 06/01/2023]
Abstract
Proteins containing a domain of unknown function 59 (DUF59) appear to have a variety of physiological functions, ranging from iron-sulfur cluster assembly to DNA repair. DUF59 proteins have been found in bacteria, archaea and eukaryotes, however Fam96a and Fam96b are the only mammalian proteins predicted to contain a DUF59 domain. Fam96a is an 18 kDa protein comprised primarily of a DUF59 domain (residues 31-157) and an N-terminal signal peptide (residues 1-27). Interestingly, the DUF59 domain of Fam96a exists as monomeric and dimeric forms in solution, and X-ray crystallography studies of both forms unexpectedly revealed two different domain-swapped dimer structures. Here we report the backbone resonance assignments and secondary structure of the monomeric form of the 127 residue DUF59 domain of human Fam96a. This study provides the basis for further understanding the structural variability exhibited by Fam96a and the mechanism for domain swapping.
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Affiliation(s)
- Caroline Mas
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
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9
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Moldoveanu T, Grace CR, Llambi F, Nourse A, Fitzgerald P, Gehring K, Kriwacki RW, Green DR. BID-induced structural changes in BAK promote apoptosis. Nat Struct Mol Biol 2013; 20:589-97. [PMID: 23604079 PMCID: PMC3683554 DOI: 10.1038/nsmb.2563] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 03/18/2013] [Indexed: 12/31/2022]
Abstract
The BCL-2 family protein BAK is responsible for mitochondrial outer membrane permeabilization (MOMP), which leads to apoptosis. The BCL-2 homology (BH) 3-only protein BID activates BAK to perform this function. We report the NMR solution structure of the human BID BH3–BAK complex, which identified the activation site at the canonical BH3-binding groove of BAK. Mutating the BAK BH1 in the groove prevented activation and MOMP but not the binding of BID. BAK BH3 mutations allowed BID binding and activation but blunted function by blocking BAK oligomerization. BAK activation follows a “hit-and-run” mechanism whereby BID dissociates from the trigger site allowing BAK oligomerization at an overlapping interface. In contrast, the BH3-only proteins NOXA and BAD are predicted to clash with the trigger site, and are not activators of BAK. These findings provide insights into the early stages of BAK activation.
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Affiliation(s)
- Tudor Moldoveanu
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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10
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Tatulian SA. Structural characterization of membrane proteins and peptides by FTIR and ATR-FTIR spectroscopy. Methods Mol Biol 2013; 974:177-218. [PMID: 23404277 DOI: 10.1007/978-1-62703-275-9_9] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Fourier transform infrared (FTIR) spectroscopy is widely used in structural characterization of proteins or peptides. While the method does not have the capability of providing the precise, atomic-resolution molecular structure, it is exquisitely sensitive to conformational changes occurring in proteins upon functional transitions or upon intermolecular interactions. Sensitivity of vibrational frequencies to atomic masses has led to development of "isotope-edited" FTIR spectroscopy, where structural effects in two proteins, one unlabeled and the other labeled with a heavier stable isotope, such as (13)C, are resolved simultaneously based on spectral downshift (separation) of the amide I band of the labeled protein. The same isotope effect is used to identify site-specific conformational changes in proteins by site-directed or segmental isotope labeling. Negligible light scattering in the infrared region provides an opportunity to study intermolecular interactions between large protein complexes, interactions of proteins and peptides with lipid vesicles, or protein-nucleic acid interactions without light scattering problems often encountered in ultraviolet spectroscopy. Attenuated total reflection FTIR (ATR-FTIR) is a surface-sensitive version of infrared spectroscopy that has proved useful in studying membrane proteins and lipids, protein-membrane interactions, mechanisms of interfacial enzymes, and molecular architecture of membrane pore or channel forming proteins and peptides. The purpose of this article was to provide a practical guide to analyze protein structure and protein-membrane interactions by FTIR and ATR-FTIR techniques, including procedures of sample preparation, measurements, and data analysis. Basic background information on FTIR spectroscopy, as well as some relatively new developments in structural and functional characterization of proteins and peptides in lipid membranes, are also presented.
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Affiliation(s)
- Suren A Tatulian
- Department of Physics, University of Central Florida, Orlando, FL, USA.
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11
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Lin H, Kitova EN, Johnson MA, Eugenio L, Ng KKS, Klassen JS. Electrospray ionization-induced protein unfolding. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:2122-2131. [PMID: 22993046 DOI: 10.1007/s13361-012-0483-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 08/08/2012] [Accepted: 08/21/2012] [Indexed: 06/01/2023]
Abstract
Electrospray ionization mass spectrometry (ESI-MS) measurements were performed under a variety of solution conditions on a highly acidic sub-fragment (B3C) of the C-terminal carbohydrate-binding repeat region of Clostridium difficile toxin B, and two mutants (B4A and B4B) containing fewer acidic residues. ESI-MS measurements performed in negative ion mode on aqueous ammonium acetate solutions of B3C at low ionic strength (I < 80 mM) revealed evidence, based on the measured charge state distribution, of protein unfolding. In contrast, no evidence of unfolding was detected from ESI-MS measurements made in positive ion mode at low I or in either mode at higher I. The results of proton nuclear magnetic resonance and circular dichroism spectroscopy measurements and gel filtration chromatography performed on solutions of B3C under low and high I conditions suggest that the protein exists predominantly in a folded state in neutral aqueous solutions with I > 10 mM. The results of ESI-MS measurements performed on B3C in a series of solutions with high I at pH 5 to 9 rule out the possibility that the structural changes are related to ESI-induced changes in pH. It is proposed that unfolding of B3C, observed in negative mode for solutions with low I, occurs during the ESI process and arises due to Coulombic repulsion between the negatively charged residues and liquid/droplet surface charge. ESI-MS measurements performed in negative ion mode on B4A and B4B also reveal a shift to higher charge states at low I but the magnitude of the changes are smaller than observed for B3C.
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Affiliation(s)
- Hong Lin
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2
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12
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Vajjhala PR, Mirams RE, Hill JM. Multiple binding sites on the pyrin domain of ASC protein allow self-association and interaction with NLRP3 protein. J Biol Chem 2012; 287:41732-43. [PMID: 23066025 DOI: 10.1074/jbc.m112.381228] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A key process underlying an innate immune response to pathogens or cellular stress is activation of members of the NOD-like receptor family, such as NLRP3, to assemble caspase-1-activating inflammasome complexes. Activated caspase-1 processes proinflammatory cytokines into active forms that mediate inflammation. Activation of the NLRP3 inflammasome is also associated with common diseases including cardiovascular disease, diabetes, chronic kidney disease, and Alzheimer disease. However, the molecular details of NLRP3 inflammasome assembly are not established. The adaptor protein ASC plays a key role in inflammasome assembly. It is composed of an N-terminal pyrin domain (PYD) and a C-terminal caspase recruitment domain, which are protein interaction domains of the death fold superfamily. ASC interacts with NLRP3 via a homotypic PYD interaction and recruits procaspase-1 via a homotypic caspase recruitment domain interaction. Here we demonstrate that ASC PYD contains two distinct binding sites important for self-association and interaction with NLRP3 and the modulatory protein POP1. Modeling of the homodimeric ASC PYD complex formed via an asymmetric interaction using both sites resembles a type I interaction found in other death fold domain complexes. This interaction mode also permits assembly of ASC PYDs into filaments. Furthermore, a type I binding mode is likely conserved in interactions with NLRP3 and POP1, because residues critical for interaction of ASC PYD are conserved in these PYDs. We also demonstrate that ASC PYD can simultaneously self-associate and interact with NLRP3, rationalizing the model whereby ASC self-association upon recruitment to NLRP3 promotes clustering and activation of procaspase-1.
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Affiliation(s)
- Parimala R Vajjhala
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia
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13
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Kumar A, Ward P, Katre UV, Mohanty S. A novel and simple method of production and biophysical characterization of a mini-membrane protein, Ost4p: a subunit of yeast oligosaccharyl transferase. Biopolymers 2012; 97:499-507. [PMID: 22302405 DOI: 10.1002/bip.22028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 12/03/2011] [Accepted: 01/13/2012] [Indexed: 11/07/2022]
Abstract
Asparagine-linked glycosylation is an essential and highly conserved protein modification reaction. In eukaryotes, oligosaccharyl transferase (OT), a multi-subunit membrane-associated enzyme complex, catalyzes this reaction in newly synthesized proteins. In Saccharomyces cerevisiae, OT consists of nine nonidentical membrane proteins. Ost4p, the smallest subunit, bridges the catalytic subunit Stt3p with Ost3p. Mutation of transmembrane residues 18-24 in Ost4p has negative effect on OT activity, disrupts the Stt3p-Ost4p-Ost3p complex, results in temperature-sensitive phenotype, and hypoglycosylation. Heterologous expression and purification of integral membrane proteins are the bottleneck in membrane protein research. The authors report the cloning, successful overexpression and purification of recombinant Ost4p with a novel but simple method producing milligram quantities of pure protein. GB1 protein was found to be the most suitable tag for the large scale production of Ost4p. The cleavage of Ost4p conveniently leaves GB1 protein in solution eliminating further purification. The precipitated pure Ost4p is reconstituted in appropriate membrane mimetic. The recombinant protein is highly helical as indicated by the far-UV CD spectrum. The well-dispersed heteronuclear single quantum coherence spectrum indicates that this minimembrane protein is well-folded. The successful production of pure recombinant Ost4p with a novel yet simple method may have important ramification for the production of other membrane proteins.
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Affiliation(s)
- Amit Kumar
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL, USA
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