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Song J, Li J, Chan HS. Small-Angle X-ray Scattering Signatures of Conformational Heterogeneity and Homogeneity of Disordered Protein Ensembles. J Phys Chem B 2021; 125:6451-6478. [PMID: 34115515 DOI: 10.1021/acs.jpcb.1c02453] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An accurate account of disordered protein conformations is of central importance to deciphering the physicochemical basis of biological functions of intrinsically disordered proteins and the folding-unfolding energetics of globular proteins. Physically, disordered ensembles of nonhomopolymeric polypeptides are expected to be heterogeneous, i.e., they should differ from those homogeneous ensembles of homopolymers that harbor an essentially unique relationship between average values of end-to-end distance REE and radius of gyration Rg. It was posited recently, however, that small-angle X-ray scattering (SAXS) data on conformational dimensions of disordered proteins can be rationalized almost exclusively by homopolymer ensembles. Assessing this perspective, chain-model simulations are used to evaluate the discriminatory power of SAXS-determined molecular form factors (MFFs) with regard to homogeneous versus heterogeneous ensembles. The general approach adopted here is not bound by any assumption about ensemble encodability, in that the postulated heterogeneous ensembles we evaluated are not restricted to those entailed by simple interaction schemes. Our analysis of MFFs for certain heterogeneous ensembles with more narrowly distributed REE and Rg indicates that while they deviate from MFFs of homogeneous ensembles, the differences can be rather small. Remarkably, some heterogeneous ensembles with asphericity and REE drastically different from those of homogeneous ensembles can nonetheless exhibit practically identical MFFs, demonstrating that SAXS MFFs do not afford unique characterizations of basic properties of conformational ensembles in general. In other words, the ensemble to MFF mapping is practically many-to-one and likely nonsmooth. Heteropolymeric variations of the REE-Rg relationship were further showcased using an analytical perturbation theory developed here for flexible heteropolymers. Ramifications of our findings for interpretation of experimental data are discussed.
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Affiliation(s)
- Jianhui Song
- School of Polymer Science and Engineering, Qingdao University of Science and Technology, 53 Zhengzhou Road, Qingdao 266042, China
| | - Jichen Li
- School of Polymer Science and Engineering, Qingdao University of Science and Technology, 53 Zhengzhou Road, Qingdao 266042, China
| | - Hue Sun Chan
- Department of Biochemistry, University of Toronto Faculty of Medicine, Toronto, Ontario M5S 1A8, Canada
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2
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Chen YW, Rahman SK. Fatal Attraction: The Case of Toxic Soluble Dimers of Truncated PQBP-1 Mutants in X-Linked Intellectual Disability. Int J Mol Sci 2021; 22:ijms22052240. [PMID: 33668121 PMCID: PMC7956452 DOI: 10.3390/ijms22052240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/20/2021] [Accepted: 02/20/2021] [Indexed: 11/16/2022] Open
Abstract
The frameshift mutants K192Sfs*7 and R153Sfs*41, of the polyglutamine tract-binding protein 1 (PQBP-1), are stable intrinsically disordered proteins (IDPs). They are each associated with the severe cognitive disorder known as the Renpenning syndrome, a form of X-linked intellectual disability (XLID). Relative to the monomeric wild-type protein, these mutants are dimeric, contain more folded contents, and have higher thermal stabilities. Comparisons can be drawn to the toxic oligomerisation in the “conformational diseases”, which collectively describe medical conditions involving a substantial protein structural transition in the pathogenic mechanism. At the molecular level, the end state of these diseases is often cytotoxic protein aggregation. The conformational disease proteins contain varying extents of intrinsic disorder, and the consensus pathogenesis includes an early oligomer formation. We reviewed the experimental characterisation of the toxic oligomers in representative cases. PQBP-1 mutant dimerisation was then compared to the oligomerisation of the conformational disease proteins. The PQBP-1 mutants are unique in behaving as stable soluble dimers, which do not further develop into higher oligomers or aggregates. The toxicity of the PQBP-1 mutant dimers lies in the native functions (in transcription regulation and possibly, RNA splicing) being compromised, rather than proceeding to aggregation. Other examples of stable IDP dimers were discussed and we speculated on the roles of IDP dimerisation in protein evolution.
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Affiliation(s)
- Yu Wai Chen
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hunghom 999077, Hong Kong
- State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hunghom 999077, Hong Kong
- Correspondence:
| | - Shah Kamranur Rahman
- Department of Infection Biology, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK;
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3
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Amin AN, Lin YH, Das S, Chan HS. Analytical Theory for Sequence-Specific Binary Fuzzy Complexes of Charged Intrinsically Disordered Proteins. J Phys Chem B 2020; 124:6709-6720. [PMID: 32639157 DOI: 10.1021/acs.jpcb.0c04575] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Intrinsically disordered proteins (IDPs) are important for biological functions. In contrast to folded proteins, molecular recognition among certain IDPs is "fuzzy" in that their binding and/or phase separation are stochastically governed by the interacting IDPs' amino acid sequences, while their assembled conformations remain largely disordered. To help elucidate a basic aspect of this fascinating yet poorly understood phenomenon, the binding of a homo or heterodimeric pair of polyampholytic IDPs is modeled statistical mechanically using cluster expansion. We find that the binding affinities of binary fuzzy complexes in the model correlate strongly with a newly derived simple "joint sequence charge decoration" parameter readily calculable from the pair of IDPs' sequence charge patterns. Predictions by our analytical theory are in essential agreement with coarse-grained explicit-chain simulations. This computationally efficient theoretical framework is expected to be broadly applicable to rationalizing and predicting sequence-specific IDP-IDP polyelectrostatic interactions.
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Affiliation(s)
- Alan N Amin
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Yi-Hsuan Lin
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Molecular Medicine, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada
| | - Suman Das
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Hue Sun Chan
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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4
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The Mammalian High Mobility Group Protein AT-Hook 2 (HMGA2): Biochemical and Biophysical Properties, and Its Association with Adipogenesis. Int J Mol Sci 2020; 21:ijms21103710. [PMID: 32466162 PMCID: PMC7279267 DOI: 10.3390/ijms21103710] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 04/30/2020] [Accepted: 05/12/2020] [Indexed: 12/11/2022] Open
Abstract
The mammalian high-mobility-group protein AT-hook 2 (HMGA2) is a small DNA-binding protein and consists of three “AT-hook” DNA-binding motifs and a negatively charged C-terminal motif. It is a multifunctional nuclear protein directly linked to obesity, human height, stem cell youth, human intelligence, and tumorigenesis. Biochemical and biophysical studies showed that HMGA2 is an intrinsically disordered protein (IDP) and could form homodimers in aqueous buffer solution. The “AT-hook” DNA-binding motifs specifically bind to the minor groove of AT-rich DNA sequences and induce DNA-bending. HMGA2 plays an important role in adipogenesis most likely through stimulating the proliferative expansion of preadipocytes and also through regulating the expression of transcriptional factor Peroxisome proliferator-activated receptor γ (PPARγ) at the clonal expansion step from preadipocytes to adipocytes. Current evidence suggests that a main function of HMGA2 is to maintain stemness and renewal capacity of stem cells by which HMGA2 binds to chromosome and lock chromosome into a specific state, to allow the human embryonic stem cells to maintain their stem cell potency. Due to the importance of HMGA2 in adipogenesis and tumorigenesis, HMGA2 is considered a potential therapeutic target for anticancer and anti-obesity drugs. Efforts are taken to identify inhibitors targeting HMGA2.
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5
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Niemeyer M, Moreno Castillo E, Ihling CH, Iacobucci C, Wilde V, Hellmuth A, Hoehenwarter W, Samodelov SL, Zurbriggen MD, Kastritis PL, Sinz A, Calderón Villalobos LIA. Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin co-receptor assemblies. Nat Commun 2020; 11:2277. [PMID: 32385295 PMCID: PMC7210949 DOI: 10.1038/s41467-020-16147-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 04/17/2020] [Indexed: 12/31/2022] Open
Abstract
Cullin RING-type E3 ubiquitin ligases SCFTIR1/AFB1-5 and their AUX/IAA targets perceive the phytohormone auxin. The F-box protein TIR1 binds a surface-exposed degron in AUX/IAAs promoting their ubiquitylation and rapid auxin-regulated proteasomal degradation. Here, by adopting biochemical, structural proteomics and in vivo approaches we unveil how flexibility in AUX/IAAs and regions in TIR1 affect their conformational ensemble allowing surface accessibility of degrons. We resolve TIR1·auxin·IAA7 and TIR1·auxin·IAA12 complex topology, and show that flexible intrinsically disordered regions (IDRs) in the degron’s vicinity, cooperatively position AUX/IAAs on TIR1. We identify essential residues at the TIR1 N- and C-termini, which provide non-native interaction interfaces with IDRs and the folded PB1 domain of AUX/IAAs. We thereby establish a role for IDRs in modulating auxin receptor assemblies. By securing AUX/IAAs on two opposite surfaces of TIR1, IDR diversity supports locally tailored positioning for targeted ubiquitylation, and might provide conformational flexibility for a multiplicity of functional states. Auxin-mediated recruitment of AUX/IAAs by the F-box protein TIR1 prompts rapid AUX/IAA ubiquitylation and degradation. By resolving auxin receptor topology, the authors show that intrinsically disordered regions near the degrons of two Aux/IAA proteins reinforce complex assembly and position Aux/IAAs for ubiquitylation.
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Affiliation(s)
- Michael Niemeyer
- Molecular Signal Processing Department, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany
| | - Elena Moreno Castillo
- Molecular Signal Processing Department, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany
| | - Christian H Ihling
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120, Halle (Saale), Germany
| | - Claudio Iacobucci
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120, Halle (Saale), Germany
| | - Verona Wilde
- Molecular Signal Processing Department, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany
| | - Antje Hellmuth
- Molecular Signal Processing Department, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany
| | - Wolfgang Hoehenwarter
- Proteome Analytics, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany
| | - Sophia L Samodelov
- Institute of Synthetic Biology & Cluster of Excellence on Plant Science (CEPLAS), Heinrich-Heine University of Düsseldorf, Universitätsstrasse 1, 40225, Düsseldorf, Germany
| | - Matias D Zurbriggen
- Institute of Synthetic Biology & Cluster of Excellence on Plant Science (CEPLAS), Heinrich-Heine University of Düsseldorf, Universitätsstrasse 1, 40225, Düsseldorf, Germany
| | - Panagiotis L Kastritis
- ZIK HALOMEM & Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Biozentrum, Weinbergweg 22, 06120, Halle (Saale), Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Charles Tanford Protein Center, Kurt-Mothes-Straße 3a, 06120, Halle (Saale), Germany
| | - Luz Irina A Calderón Villalobos
- Molecular Signal Processing Department, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, 06120, Halle (Saale), Germany.
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6
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Das T, Eliezer D. Membrane interactions of intrinsically disordered proteins: The example of alpha-synuclein. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2019; 1867:879-889. [PMID: 31096049 PMCID: PMC6661188 DOI: 10.1016/j.bbapap.2019.05.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 05/03/2019] [Accepted: 05/08/2019] [Indexed: 12/11/2022]
Abstract
Peripheral membrane proteins associate reversibly with biological membranes that, compared to protein binding partners, are structurally labile and devoid of specific binding pockets. Membranes in different subcellular compartments vary primarily in their chemical composition and physical properties, and recognition of these features is therefore critical for allowing such proteins to engage their proper membrane targets. Intrinsically disordered proteins (IDPs) are well-suited to accomplish this task using highly specific and low- to moderate-affinity interactions governed by recognition principles that are both similar to and different from those that mediate the membrane interactions of rigid proteins. IDPs have also evolved multiple mechanisms to regulate membrane (and other) interactions and achieve their impressive functional diversity. Moreover, IDP-membrane interactions may have a kinetic advantage in fast processes requiring rapid control of such interactions, such as synaptic transmission or signaling. Herein we review the biophysics, regulation and functional implications of IDP-membrane interactions and include a brief overview of some of the methods that can be used to study such interactions. At each step, we use the example of alpha-synuclein, a protein involved in the pathogenesis of Parkinson's disease and one of the best characterized membrane-binding IDP, to illustrate some of the principles discussed.
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Affiliation(s)
- Tapojyoti Das
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, United States of America
| | - David Eliezer
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, United States of America.
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7
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The Structural and Functional Diversity of Intrinsically Disordered Regions in Transmembrane Proteins. J Membr Biol 2019; 252:273-292. [DOI: 10.1007/s00232-019-00069-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 05/17/2019] [Indexed: 10/26/2022]
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8
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Mendes LFS, Fontana NA, Oliveira CG, Freire MCLC, Lopes JLS, Melo FA, Costa‐Filho AJ. The
GRASP
domain in golgi reassembly and stacking proteins: differences and similarities between lower and higher Eukaryotes. FEBS J 2019; 286:3340-3358. [DOI: 10.1111/febs.14869] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/18/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Luís F. S. Mendes
- Departamento de Física Faculdade de Filosofia Ciências e Letras de Ribeirão Preto Universidade de São Paulo Ribeirão Preto Brazil
| | - Natália A. Fontana
- Departamento de Física Faculdade de Filosofia Ciências e Letras de Ribeirão Preto Universidade de São Paulo Ribeirão Preto Brazil
| | - Carolina G. Oliveira
- Departamento de Física Faculdade de Filosofia Ciências e Letras de Ribeirão Preto Universidade de São Paulo Ribeirão Preto Brazil
| | | | - José L. S. Lopes
- Departamento de Física Aplicada Instituto de Física Universidade de São Paulo São Paulo Brazil
| | - Fernando A. Melo
- Departamento de Física Centro Multiusuário de Inovação Biomolecular IBILCE Universidade Estadual Paulista Júlio Mesquita São Paulo Brazil
| | - Antonio J. Costa‐Filho
- Departamento de Física Faculdade de Filosofia Ciências e Letras de Ribeirão Preto Universidade de São Paulo Ribeirão Preto Brazil
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9
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Więch A, Rowińska-Żyrek M, Wątły J, Czarnota A, Hołubowicz R, Szewczuk Z, Ożyhar A, Orłowski M. The intrinsically disordered C-terminal F domain of the ecdysteroid receptor from Aedes aegypti exhibits metal ion-binding ability. J Steroid Biochem Mol Biol 2019; 186:42-55. [PMID: 30243841 DOI: 10.1016/j.jsbmb.2018.09.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/29/2018] [Accepted: 09/12/2018] [Indexed: 11/18/2022]
Abstract
The dominant vector of dengue and Zika diseases is a female Aedes aegypti mosquito. Its reproduction is controlled by the formation of an active heterodimer complex of the 20-hydroxyecdysone receptor (EcR) and Ultraspiracle protein (Usp). Although EcR exhibits a structural and functional organization typical of nuclear receptors (NRs), the EcR C-terminus has an additional F domain (AaFEcR) that is rarely present in the NRs superfamily. The presence of F domains is evolutionarily not well conserved in the NRs. The structure-function relationship of EcR F domains in arthropods is unclear and enigmatic. To date, there have been no data concerning the structure and function of AaFEcR. Our results showed that AaFEcR belongs to a family of intrinsically disordered proteins (IDPs) and possesses putative pre-molten globule (PMG) characteristics. Unexpectedly, additional amino acid composition in silico analyses revealed the presence of short unique repeated Pro-His clusters forming an HGPHPHPHG motif, which is similar to those responsible for Zn2+ and Cu2+ binding in histidine-proline-rich glycoproteins (HPRGs). Using SEC, SV-AUC and ESI-TOF MS, we showed that the intrinsically disordered AaFEcR is able to bind metal ions and form complexes with these ions. Our studies provide new insight into the structural organization and activities of the F domains of NRs. This unique for the F domains of NRs ion-binding propensity demonstrated by the AaFEcR domain may be a part of the ecdysteroid receptor's mechanism for regulating the expression of genes encoding oxidative stress-protecting proteins.
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Affiliation(s)
- Anna Więch
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | | | - Joanna Wątły
- Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland
| | - Aleksandra Czarnota
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Rafał Hołubowicz
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | | | - Andrzej Ożyhar
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Marek Orłowski
- Department of Biochemistry, Faculty of Chemistry, Wrocław University of Science and Technology, 50-370 Wrocław, Poland.
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10
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Targeting Intramembrane Protein-Protein Interactions: Novel Therapeutic Strategy of Millions Years Old. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2018; 111:61-99. [PMID: 29459036 PMCID: PMC7102818 DOI: 10.1016/bs.apcsb.2017.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Intramembrane protein-protein interactions (PPIs) are involved in transmembrane signal transduction mediated by cell surface receptors and play an important role in health and disease. Recently, receptor-specific modulatory peptides rationally designed using a general platform of transmembrane signaling, the signaling chain homooligomerization (SCHOOL) model, have been proposed to therapeutically target these interactions in a variety of serious diseases with unmet needs including cancer, sepsis, arthritis, retinopathy, and thrombosis. These peptide drug candidates use ligand-independent mechanisms of action (SCHOOL mechanisms) and demonstrate potent efficacy in vitro and in vivo. Recent studies surprisingly revealed that in order to modify and/or escape the host immune response, human viruses use similar mechanisms and modulate cell surface receptors by targeting intramembrane PPIs in a ligand-independent manner. Here, I review these intriguing mechanistic similarities and discuss how the viral strategies optimized over a billion years of the coevolution of viruses and their hosts can help to revolutionize drug discovery science and develop new, disruptive therapies. Examples are given.
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11
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Bahramali G, Goliaei B, Minuchehr Z, Marashi SA. A network biology approach to understanding the importance of chameleon proteins in human physiology and pathology. Amino Acids 2016; 49:303-315. [DOI: 10.1007/s00726-016-2361-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 11/05/2016] [Indexed: 12/20/2022]
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12
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Neira JL, Martínez-Rodríguez S, Hernández-Cifre JG, Cámara-Artigas A, Clemente P, Peralta S, Fernández-Moreno MÁ, Garesse R, García de la Torre J, Rizzuti B. Human COA3 Is an Oligomeric Highly Flexible Protein in Solution. Biochemistry 2016; 55:6209-6220. [PMID: 27791355 DOI: 10.1021/acs.biochem.6b00644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The assembly of the protein complex of cytochrome c oxidase (COX), which participates in the mitochondrial respiratory chain, requires a large number of accessory proteins (the so-called assembly factors). Human COX assembly factor 3 (hCOA3), also known as MITRAC12 or coiled-coil domain-containing protein 56 (CCDC56), interacts with the first subunit protein of COX to form its catalytic core and promotes its assemblage with the other units. Therefore, hCOA3 is involved in COX biogenesis in humans and can be exploited as a drug target in patients with mitochondrial dysfunctions. However, to be considered a molecular target, its structure and conformational stability must first be elucidated. We have embarked on the description of such features by using spectroscopic and hydrodynamic techniques, in aqueous solution and in the presence of detergents, together with computational methods. Our results show that hCOA3 is an oligomeric protein, forming aggregates of different molecular masses in aqueous solution. Moreover, on the basis of fluorescence and circular dichroism results, the protein has (i) its unique tryptophan partially shielded from solvent and (ii) a relatively high percentage of secondary structure. However, this structure is highly flexible and does not involve hydrogen bonding. Experiments in the presence of detergents suggest a slightly higher content of nonrigid helical structure. Theoretical results, based on studies of the primary structure of the protein, further support the idea that hCOA3 is a disordered protein. We suggest that the flexibility of hCOA3 is crucial for its interaction with other proteins to favor mitochondrial protein translocation and assembly of proteins involved in the respiratory chain.
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Affiliation(s)
- José L Neira
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , Elche, Alicante, Spain.,Biocomputation and Complex Systems Physics Institute , Zaragoza, Spain
| | | | | | - Ana Cámara-Artigas
- Department of Chemistry and Physics, University of Almería , Agrifood Campus of International Excellence (ceiA3), Almería, Spain
| | - Paula Clemente
- Departamento de Bioquímica-Instituto de Investigaciones Biomédicas "Alberto Sols", Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) , Madrid, Spain.,Instituto de Investigación Sanitaria, Hospital 12 de Octubre (i+12) , Madrid, Spain
| | - Susana Peralta
- Departamento de Bioquímica-Instituto de Investigaciones Biomédicas "Alberto Sols", Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) , Madrid, Spain.,Instituto de Investigación Sanitaria, Hospital 12 de Octubre (i+12) , Madrid, Spain
| | - Miguel Ángel Fernández-Moreno
- Departamento de Bioquímica-Instituto de Investigaciones Biomédicas "Alberto Sols", Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) , Madrid, Spain.,Instituto de Investigación Sanitaria, Hospital 12 de Octubre (i+12) , Madrid, Spain
| | - Rafael Garesse
- Departamento de Bioquímica-Instituto de Investigaciones Biomédicas "Alberto Sols", Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) , Madrid, Spain.,Instituto de Investigación Sanitaria, Hospital 12 de Octubre (i+12) , Madrid, Spain
| | | | - Bruno Rizzuti
- CNR-NANOTEC, Licryl-UOS Cosenza and CEMIF.Cal, Department of Physics, University of Calabria , 87036 Rende, Italy
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