1
|
Harihar B, Saravanan KM, Gromiha MM, Selvaraj S. Importance of Inter-residue Contacts for Understanding Protein Folding and Unfolding Rates, Remote Homology, and Drug Design. Mol Biotechnol 2024:10.1007/s12033-024-01119-4. [PMID: 38498284 DOI: 10.1007/s12033-024-01119-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Accepted: 02/10/2024] [Indexed: 03/20/2024]
Abstract
Inter-residue interactions in protein structures provide valuable insights into protein folding and stability. Understanding these interactions can be helpful in many crucial applications, including rational design of therapeutic small molecules and biologics, locating functional protein sites, and predicting protein-protein and protein-ligand interactions. The process of developing machine learning models incorporating inter-residue interactions has been improved recently. This review highlights the theoretical models incorporating inter-residue interactions in predicting folding and unfolding rates of proteins. Utilizing contact maps to depict inter-residue interactions aids researchers in developing computer models for detecting remote homologs and interface residues within protein-protein complexes which, in turn, enhances our knowledge of the relationship between sequence and structure of proteins. Further, the application of contact maps derived from inter-residue interactions is highlighted in the field of drug discovery. Overall, this review presents an extensive assessment of the significant models that use inter-residue interactions to investigate folding rates, unfolding rates, remote homology, and drug development, providing potential future advancements in constructing efficient computational models in structural biology.
Collapse
Affiliation(s)
- Balasubramanian Harihar
- Department of Bioinformatics, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Konda Mani Saravanan
- Department of Bioinformatics, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India
- Department of Biotechnology, Bharath Institute of Higher Education and Research, Chennai, Tamil Nadu, 600073, India
| | - Michael M Gromiha
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Samuel Selvaraj
- Department of Bioinformatics, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024, India.
| |
Collapse
|
2
|
Zhou Q, Liu X, Neri D, Li W, Favalli N, Bassi G, Yang S, Yang D, Vogt PK, Wang MW. Structural insights into the interaction of three Y-shaped ligands with PI3Kα. Proc Natl Acad Sci U S A 2023; 120:e2304071120. [PMID: 37585458 PMCID: PMC10450665 DOI: 10.1073/pnas.2304071120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 07/19/2023] [Indexed: 08/18/2023] Open
Abstract
Class IA phosphoinositide 3-kinase alpha (PI3Kα) is an important drug target because it is one of the most frequently mutated proteins in human cancers. However, small molecule inhibitors currently on the market or under development have safety concerns due to a lack of selectivity. Therefore, other chemical scaffolds or unique mechanisms of catalytic kinase inhibition are needed. Here, we report the cryo-electron microscopy structures of wild-type PI3Kα, the dimer of p110α and p85α, in complex with three Y-shaped ligands [cpd16 (compound 16), cpd17 (compound 17), and cpd18 (compound 18)] of different affinities and no inhibitory effect on the kinase activity. Unlike ATP-competitive inhibitors, cpd17 adopts a Y-shaped conformation with one arm inserted into a binding pocket formed by R770 and W780 and the other arm lodged in the ATP-binding pocket at an angle that is different from that of the ATP phosphate tail. Such a special interaction induces a conformation of PI3Kα resembling that of the unliganded protein. These observations were confirmed with two isomers (cpd16 and cpd18). Further analysis of these Y-shaped ligands revealed the structural basis of differential binding affinities caused by stereo- or regiochemical modifications. Our results may offer a different direction toward the design of therapeutic agents against PI3Kα.
Collapse
Affiliation(s)
- Qingtong Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
| | - Xiao Liu
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
| | - Dario Neri
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich8093, Switzerland
| | - Wenxin Li
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
| | - Nicholas Favalli
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich8093, Switzerland
| | - Gabriele Bassi
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zurich), Zurich8093, Switzerland
| | - Su Yang
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA92037
| | - Dehua Yang
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai201203, China
| | - Peter K. Vogt
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA92037
| | - Ming-Wei Wang
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai200032, China
- Research Center for Deepsea Bioresources, Sanya572025, China
- Department of Chemistry, School of Science, The University of Tokyo, Tokyo113-0033, Japan
- School of Pharmacy, Hainan Medical College, Haikou570228, China
| |
Collapse
|
3
|
Anwar M, Haseeb M, Choi S, Kim KP. P176S Mutation Rewires Electrostatic Interactions That Alter Maspin Functionality. ACS OMEGA 2023; 8:28258-28267. [PMID: 37576651 PMCID: PMC10413834 DOI: 10.1021/acsomega.3c01850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 06/21/2023] [Indexed: 08/15/2023]
Abstract
Maspin is known to regress tumors by inhibiting angiogenesis; however, its roles have been reported to be context- and sequence-dependent. Various proteins and cofactors bind to maspin, possibly explaining its conflicting roles. Moreover, polymorphic forms of maspin have also been linked to tumor regression and survival; for instance, maspin with Ser at 176 (maspin-S176) promotes tumors, while maspin with Pro at 176 (maspin-P176) has opposing roles in cancer pathogenesis. With the help of long molecular dynamics simulations, a possible link between polymorphic forms and tumor progression has been established. First, maspin is dynamically stable with either amino acid at the 176 position. Second, differential contacts have been observed among various regions; third, these contacts have significantly altered the electrostatic energetics of various residues; finally, these altered electrostatics of maspin-S176 and maspin-P176 rewire the polar contacts that abolished the allosteric control of the protein. By combining these factors, the altered electrostatics substantially affect the localization and preference of maspin-binding partners, thus culminating in a different maspin-protein(cofactor)-interaction landscape that may have been manifested in previous conflicting reports. Here, the underlying reason has been highlighted and discussed, which may be helpful for better therapeutic manipulation.
Collapse
Affiliation(s)
- Muhammad
Ayaz Anwar
- Department
of Applied Chemistry, Institute of Natural Science, Global Center
for Pharmaceutical Ingredient Materials, Kyung Hee University, Yongin 17104, Republic
of Korea
| | - Muhammad Haseeb
- Department
of Molecular Science and Technology, Ajou
University, Suwon 16499, Republic
of Korea
| | - Sangdun Choi
- Department
of Molecular Science and Technology, Ajou
University, Suwon 16499, Republic
of Korea
| | - Kwang Pyo Kim
- Department
of Applied Chemistry, Institute of Natural Science, Global Center
for Pharmaceutical Ingredient Materials, Kyung Hee University, Yongin 17104, Republic
of Korea
- Department
of Biomedical Science and Technology, Kyung
Hee Medical Science Research Institute, Kyung Hee University, Seoul 02447, Republic of Korea
| |
Collapse
|
4
|
Guloglu B, Deane CM. Specific attributes of the V L domain influence both the structure and structural variability of CDR-H3 through steric effects. Front Immunol 2023; 14:1223802. [PMID: 37564639 PMCID: PMC10410447 DOI: 10.3389/fimmu.2023.1223802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/28/2023] [Indexed: 08/12/2023] Open
Abstract
Antibodies, through their ability to target virtually any epitope, play a key role in driving the adaptive immune response in jawed vertebrates. The binding domains of standard antibodies are their variable light (VL) and heavy (VH) domains, both of which present analogous complementarity-determining region (CDR) loops. It has long been known that the VH CDRs contribute more heavily to the antigen-binding surface (paratope), with the CDR-H3 loop providing a major modality for the generation of diverse paratopes. Here, we provide evidence for an additional role of the VL domain as a modulator of CDR-H3 structure, using a diverse set of antibody crystal structures and a large set of molecular dynamics simulations. We show that specific attributes of the VL domain such as subtypes, CDR canonical forms and genes can influence the structural diversity of the CDR-H3 loop, and provide a physical model for how this effect occurs through inter-loop contacts and packing of CDRs against each other. Our results indicate that the rigid minor loops fine-tune the structure of CDR-H3, thereby contributing to the generation of surfaces complementary to the vast number of possible epitope topologies, and provide insights into the interdependent nature of CDR conformations, an understanding of which is important for the rational antibody design process.
Collapse
Affiliation(s)
- Bora Guloglu
- Oxford Protein Informatics Group, Department of Statistics, University of Oxford, Oxford, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford, United Kingdom
| | - Charlotte M. Deane
- Oxford Protein Informatics Group, Department of Statistics, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
5
|
Mi X, Desormeaux EK, Le TT, van der Donk WA, Shukla D. Sequence controlled secondary structure is important for the site-selectivity of lanthipeptide cyclization. Chem Sci 2023; 14:6904-6914. [PMID: 37389248 PMCID: PMC10306099 DOI: 10.1039/d2sc06546k] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 05/08/2023] [Indexed: 07/01/2023] Open
Abstract
Lanthipeptides are ribosomally synthesized and post-translationally modified peptides that are generated from precursor peptides through a dehydration and cyclization process. ProcM, a class II lanthipeptide synthetase, demonstrates high substrate tolerance. It is enigmatic that a single enzyme can catalyze the cyclization process of many substrates with high fidelity. Previous studies suggested that the site-selectivity of lanthionine formation is determined by substrate sequence rather than by the enzyme. However, exactly how substrate sequence contributes to site-selective lanthipeptide biosynthesis is not clear. In this study, we performed molecular dynamic simulations for ProcA3.3 variants to explore how the predicted solution structure of the substrate without enzyme correlates to the final product formation. Our simulation results support a model in which the secondary structure of the core peptide is important for the final product's ring pattern for the substrates investigated. We also demonstrate that the dehydration step in the biosynthesis pathway does not influence the site-selectivity of ring formation. In addition, we performed simulation for ProcA1.1 and 2.8, which are well-suited candidates to investigate the connection between order of ring formation and solution structure. Simulation results indicate that in both cases, C-terminal ring formation is more likely which was supported by experimental results. Our findings indicate that the substrate sequence and its solution structure can be used to predict the site-selectivity and order of ring formation, and that secondary structure is a crucial factor influencing the site-selectivity. Taken together, these findings will facilitate our understanding of the lanthipeptide biosynthetic mechanism and accelerate bioengineering efforts for lanthipeptide-derived products.
Collapse
Affiliation(s)
- Xuenan Mi
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
| | - Emily K Desormeaux
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
| | - Tung T Le
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
| | - Wilfred A van der Donk
- Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
| | - Diwakar Shukla
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
| |
Collapse
|
6
|
Iqbal S, Brünger T, Pérez-Palma E, Macnee M, Brunklaus A, Daly MJ, Campbell AJ, Hoksza D, May P, Lal D. Delineation of functionally essential protein regions for 242 neurodevelopmental genes. Brain 2023; 146:519-533. [PMID: 36256779 PMCID: PMC9924913 DOI: 10.1093/brain/awac381] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/12/2022] [Accepted: 09/04/2022] [Indexed: 01/25/2023] Open
Abstract
Neurodevelopmental disorders (NDDs), including severe paediatric epilepsy, autism and intellectual disabilities are heterogeneous conditions in which clinical genetic testing can often identify a pathogenic variant. For many of them, genetic therapies will be tested in this or the coming years in clinical trials. In contrast to first-generation symptomatic treatments, the new disease-modifying precision medicines require a genetic test-informed diagnosis before a patient can be enrolled in a clinical trial. However, even in 2022, most identified genetic variants in NDD genes are 'variants of uncertain significance'. To safely enrol patients in precision medicine clinical trials, it is important to increase our knowledge about which regions in NDD-associated proteins can 'tolerate' missense variants and which ones are 'essential' and will cause a NDD when mutated. In addition, knowledge about functionally indispensable regions in the 3D structure context of proteins can also provide insights into the molecular mechanisms of disease variants. We developed a novel consensus approach that overlays evolutionary, and population based genomic scores to identify 3D essential sites (Essential3D) on protein structures. After extensive benchmarking of AlphaFold predicted and experimentally solved protein structures, we generated the currently largest expert curated protein structure set for 242 NDDs and identified 14 377 Essential3D sites across 189 gene disorders associated proteins. We demonstrate that the consensus annotation of Essential3D sites improves prioritization of disease mutations over single annotations. The identified Essential3D sites were enriched for functional features such as intermembrane regions or active sites and discovered key inter-molecule interactions in protein complexes that were otherwise not annotated. Using the currently largest autism, developmental disorders, and epilepsies exome sequencing studies including >360 000 NDD patients and population controls, we found that missense variants at Essential3D sites are 8-fold enriched in patients. In summary, we developed a comprehensive protein structure set for 242 NDDs and identified 14 377 Essential3D sites in these. All data are available at https://es-ndd.broadinstitute.org for interactive visual inspection to enhance variant interpretation and development of mechanistic hypotheses for 242 NDDs genes. The provided resources will enhance clinical variant interpretation and in silico drug target development for NDD-associated genes and encoded proteins.
Collapse
Affiliation(s)
- Sumaiya Iqbal
- The Center for the Development of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Tobias Brünger
- Cologne Center for Genomics, University of Cologne, 50923 Köln, Germany
| | - Eduardo Pérez-Palma
- Universidad del Desarrollo, Centro de Genética y Genómica, Facultad de Medicina Clínica Alemana, 7610658 Las Condes, Santiago de Chile, Chile
| | - Marie Macnee
- Cologne Center for Genomics, University of Cologne, 50923 Köln, Germany
| | - Andreas Brunklaus
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow G12 8QQ, UK
- School of Health and Wellbeing, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | - Mark J Daly
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA 02114, USA
- Institute for Molecular Medicine Finland (FIMM), Centre of Excellence in Complex Disease Genetics, University of Helsinki, 00100 Helsinki, Finland
| | - Arthur J Campbell
- The Center for the Development of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - David Hoksza
- Department of Software Engineering, Faculty of Mathematics and Physics, Charles University, 110 00 Staré Město, Czechia, Czech Republic
| | - Patrick May
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 4365 Esch-sur-Alzette, Luxembourg
| | - Dennis Lal
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Cologne Center for Genomics, University of Cologne, 50923 Köln, Germany
- Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH 44195, USA
- Genomic Medicine Institute, Lerner Research Institute Cleveland Clinic, Cleveland, OH 44106, USA
| |
Collapse
|
7
|
Kagaya Y, Flannery ST, Jain A, Kihara D. ContactPFP: Protein Function Prediction Using Predicted Contact Information. FRONTIERS IN BIOINFORMATICS 2022; 2. [PMID: 35875419 PMCID: PMC9302406 DOI: 10.3389/fbinf.2022.896295] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Computational function prediction is one of the most important problems in bioinformatics as elucidating the function of genes is a central task in molecular biology and genomics. Most of the existing function prediction methods use protein sequences as the primary source of input information because the sequence is the most available information for query proteins. There are attempts to consider other attributes of query proteins. Among these attributes, the three-dimensional (3D) structure of proteins is known to be very useful in identifying the evolutionary relationship of proteins, from which functional similarity can be inferred. Here, we report a novel protein function prediction method, ContactPFP, which uses predicted residue-residue contact maps as input structural features of query proteins. Although 3D structure information is known to be useful, it has not been routinely used in function prediction because the 3D structure is not experimentally determined for many proteins. In ContactPFP, we overcome this limitation by using residue-residue contact prediction, which has become increasingly accurate due to rapid development in the protein structure prediction field. ContactPFP takes a query protein sequence as input and uses predicted residue-residue contact as a proxy for the 3D protein structure. To characterize how predicted contacts contribute to function prediction accuracy, we compared the performance of ContactPFP with several well-established sequence-based function prediction methods. The comparative study revealed the advantages and weaknesses of ContactPFP compared to contemporary sequence-based methods. There were many cases where it showed higher prediction accuracy. We examined factors that affected the accuracy of ContactPFP using several illustrative cases that highlight the strength of our method.
Collapse
Affiliation(s)
- Yuki Kagaya
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
| | - Sean T. Flannery
- Department of Computer Science, Purdue University, West Lafayette, IN, United States
| | - Aashish Jain
- Department of Computer Science, Purdue University, West Lafayette, IN, United States
| | - Daisuke Kihara
- Department of Biological Sciences, Purdue University, West Lafayette, IN, United States
- Department of Computer Science, Purdue University, West Lafayette, IN, United States
- *Correspondence: Daisuke Kihara,
| |
Collapse
|
8
|
Rajendran M, Ferran MC, Babbitt GA. Identifying vaccine escape sites via statistical comparisons of short-term molecular dynamics. BIOPHYSICAL REPORTS 2022; 2:100056. [PMID: 35403093 PMCID: PMC8978532 DOI: 10.1016/j.bpr.2022.100056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 03/31/2022] [Indexed: 01/08/2023]
Abstract
The identification of viral mutations that confer escape from antibodies is crucial for understanding the interplay between immunity and viral evolution. We describe a molecular dynamics (MD)-based approach that goes beyond contact mapping, scales well to a desktop computer with a modern graphics processor, and enables the user to identify functional protein sites that are prone to vaccine escape in a viral antigen. We first implement our MD pipeline to employ site-wise calculation of Kullback-Leibler divergence in atom fluctuation over replicate sets of short-term MD production runs thus enabling a statistical comparison of the rapid motion of influenza hemagglutinin (HA) in both the presence and absence of three well-known neutralizing antibodies. Using this simple comparative method applied to motions of viral proteins, we successfully identified in silico all previously empirically confirmed sites of escape in influenza HA, predetermined via selection experiments and neutralization assays. Upon the validation of our computational approach, we then surveyed potential hotspot residues in the receptor binding domain of the SARS-CoV-2 virus in the presence of COVOX-222 and S2H97 antibodies. We identified many single sites in the antigen-antibody interface that are similarly prone to potential antibody escape and that match many of the known sites of mutations arising in the SARS-CoV-2 variants of concern. In the Omicron variant, we find only minimal adaptive evolutionary shifts in the functional binding profiles of both antibodies. In summary, we provide an inexpensive and accurate computational method to monitor hotspots of functional evolution in antibody binding footprints.
Collapse
|
9
|
Sang Z, Xiang Y, Bahar I, Shi Y. Llamanade: An open-source computational pipeline for robust nanobody humanization. Structure 2022; 30:418-429.e3. [PMID: 34895471 DOI: 10.1016/j.str.2021.11.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 09/21/2021] [Accepted: 11/17/2021] [Indexed: 12/15/2022]
Abstract
Nanobodies (Nbs) have emerged as a promising class of biologics. Despite having marked physicochemical properties, Nbs are derived from camelids and may require humanization to improve translational potentials. By systematically analyzing the sequence and structural properties of Nbs, we found substantial framework diversities and revealed the key differences between Nbs and human immunoglobulin G antibodies. We identified conserved residues that may contribute to enhanced solubility, structural stability, and antigen binding, providing insights into Nb humanization. Based on big data analysis, we developed "Llamanade," an open-source software to facilitate rational humanization of Nbs. Using sequence as input, Llamanade can rapidly extract sequence features, model structures, and optimize solutions to humanize Nbs. Finally, we used Llamanade to successfully humanize a cohort of structurally diverse and potent SARS-CoV-2 neutralizing Nbs. Llamanade is freely available and will be easily accessible on a server to support the development of therapeutic Nbs into safe and effective trials.
Collapse
Affiliation(s)
- Zhe Sang
- Department of Cell Biology, Pittsburgh, PA, USA; Department Computational and Systems Biology, Pittsburgh, PA, USA; University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA
| | - Yufei Xiang
- Department of Cell Biology, Pittsburgh, PA, USA
| | - Ivet Bahar
- Department Computational and Systems Biology, Pittsburgh, PA, USA; University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA
| | - Yi Shi
- Department of Cell Biology, Pittsburgh, PA, USA; University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA.
| |
Collapse
|
10
|
Holland J, Grigoryan G. Structure‐conditioned amino‐acid couplings: how contact geometry affects pairwise sequence preferences. Protein Sci 2022; 31:900-917. [PMID: 35060221 PMCID: PMC8927866 DOI: 10.1002/pro.4280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 01/06/2022] [Accepted: 01/12/2022] [Indexed: 11/11/2022]
Abstract
Relating a protein's sequence to its conformation is a central challenge for both structure prediction and sequence design. Statistical contact potentials, as well as their more descriptive versions that account for side‐chain orientation and other geometric descriptors, have served as simplistic but useful means of representing second‐order contributions in sequence–structure relationships. Here we ask what happens when a pairwise potential is conditioned on the fully defined geometry of interacting backbones fragments. We show that the resulting structure‐conditioned coupling energies more accurately reflect pair preferences as a function of structural contexts. These structure‐conditioned energies more reliably encode native sequence information and more highly correlate with experimentally determined coupling energies. Clustering a database of interaction motifs by structure results in ensembles of similar energies and clustering them by energy results in ensembles of similar structures. By comparing many pairs of interaction motifs and showing that structural similarity and energetic similarity go hand‐in‐hand, we provide a tangible link between modular sequence and structure elements. This link is applicable to structural modeling, and we show that scoring CASP models with structured‐conditioned energies results in substantially higher correlation with structural quality than scoring the same models with a contact potential. We conclude that structure‐conditioned coupling energies are a good way to model the impact of interaction geometry on second‐order sequence preferences.
Collapse
Affiliation(s)
- Jack Holland
- Department of Computer Science Dartmouth College Hanover New Hampshire USA
| | - Gevorg Grigoryan
- Department of Computer Science Dartmouth College Hanover New Hampshire USA
| |
Collapse
|
11
|
Hidden electrostatic energy contributions define dynamic allosteric communications within p53 during molecular recognition. Biophys J 2021; 120:4512-4524. [PMID: 34478701 DOI: 10.1016/j.bpj.2021.08.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 04/03/2021] [Accepted: 08/26/2021] [Indexed: 12/15/2022] Open
Abstract
Molecular recognition is fundamental to transcription regulation. As a transcription factor, the tumor suppressor p53 has to recognize either specific DNA sequences or repressor protein partners. However, the molecular mechanism underlying the p53 conformational switch from the DNA-bound to repressor-bound states is not fully characterized. The highly charged nature of these interacting molecules prompted us to explore the nonbonded energy contributions behind molecular recognition of either a DNA or the repressor protein iASPP by p53 DNA binding domain (p53DBD), using molecular dynamics simulation followed by rigorous analyses of energy terms. Our results illuminate the allosteric pathway by which iASPP binding to p53 diminishes binding affinity between p53 and DNA. Even though the p53DBD uses a common framework of residues for recognizing both DNA and iASPP, a comparison of the electrostatics in the two p53DBD complexes revealed significant differences in residue-wise contributions to the electrostatic energy. We found that an electrostatic allosteric communication path exists in the presence of both substrates. It consists of evolutionarily conserved residues, from residue K120 of the binding loop L1 to a distal residue R213 of p53DBD. K120 is near the DNA in the p53DBD-DNA complex, whereas iASPP binding moves it away from its DNA binding position in the p53DBD-iASPP complex. The "energy hubs" (the residues show a higher degree of connectivity with other residues in the electrostatic networks) determined from the electrostatic network analysis established that this conformational change in K120 completely rewires the electrostatic network from K120 to R213, thereby impeding DNA binding. Furthermore, we found shifting populations of hydrogen bonds and salt bridges reduce pairwise electrostatic energies within p53DBD in its DNA-bound state.
Collapse
|
12
|
In silico study of intrinsic dynamics of full-length apo-ACE2 and RBD-ACE2 complex. Comput Struct Biotechnol J 2021; 19:5455-5465. [PMID: 34603638 PMCID: PMC8479424 DOI: 10.1016/j.csbj.2021.09.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/27/2021] [Accepted: 09/27/2021] [Indexed: 11/21/2022] Open
Abstract
The key step for SARS-CoV-2 to infect human cells is the membrane fusion triggered by the binding of the viral extracellular Spike protein to the human extracellular receptor, the angiotensin-converting enzyme 2 (ACE2). Although the Cryo-electron microscopy (Cryo-EM) uncovered the static atomic details of ACE2 homodimers, there is still a lack of research on the kinetic and thermodynamic properties of these full-length structures. This information is helpful to understand and interpret the role of ACE2 in the cell entry of SARS-CoV-2. In order to obtain this information, we performed microsecond-scale conventional and accelerated molecular dynamics (MD) simulations of full-length all-atomic systems of the RBD-ACE2 complex, the normal and torsional conformations of the apo-ACE2 homodimer. The comparative analysis of these systems showed that there were differences in their allosteric signal pathways and motion trends. These results may be helpful to further explore the cell entry mechanism of SARS-CoV-2. Moreover, the binding free energy and hydrogen bond distribution analysis of RBD-ACE2 binding interface provided the binding motifs that may be critical to allosteric signal transmission and RBD binding. These multi-conformational binding motifs can be used as targets or templates for the inhibitor design of the cell entry of SARS-CoV-2.
Collapse
|
13
|
Sang Z, Xiang Y, Bahar I, Shi Y. Llamanade : an open-source computational pipeline for robust nanobody humanization. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2021:2021.08.03.455003. [PMID: 34373858 PMCID: PMC8351782 DOI: 10.1101/2021.08.03.455003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Nanobodies (Nbs) have recently emerged as a promising class of antibody fragments for biomedical and therapeutic applications. Despite having marked physicochemical properties, Nbs are derived from camelids and may require "humanization" to improve translational potentials for clinical trials. Here we have systematically analyzed the sequence and structural properties of Nbs based on NGS (next-generation sequencing) databases and high-resolution structures. Our analysis reveals substantial framework diversities and underscores the key differences between Nbs and human Immunoglobulin G (IgG) antibodies. We identified conserved residues that may contribute to enhanced solubility, structural stability, and antigen-binding, providing insights into Nb humanization. Based on big data analysis, we developed " Llamanade '', a user-friendly, open-source to facilitate rational humanization of Nbs. Using Nb sequence as input, Llamanade provides information on the sequence features, model structures, and optimizes solutions to humanize Nbs. The full analysis for a given Nb takes less than a minute on a local computer. To demonstrate the robustness of this tool, we applied it to successfully humanize a cohort of structurally diverse and highly potent SARS-CoV-2 neutralizing Nbs. Llamanade is freely available and will be easily accessible on a web server to support the development of a rapidly expanding repertoire of therapeutic Nbs into safe and effective trials. AUTHOR SUMMARY Camelid Nbs are characterized by small size, excellent pharmacological properties and high flexibility in bioengineering for therapeutic development. However, Nbs are "xeno" antibodies, which require "humanization" to improve their translational potential. Currently, there is a lack of systematic investigation of Nbs to rationally guide humanization. No dedicated software has been developed for this purpose. Here, we report the development of Llamanade , an open-source computational pipeline and the first dedicated software to facilitate rational humanization of Nbs. To subjectively evaluate Llamanade , we used it to humanize a cohort of structurally diverse and ultrapotent antiviral Nbs against SARS-CoV-2. Robust humanization by Llamanade significantly improved the humanness level of Nbs to closely resemble fully human IgGs. Importantly, these highly humanized antiviral Nbs remained excellent solubility and comparably high bioactivities to the non-humanized Nb precursors. We envision that Llamanade will help advance Nb research into therapeutic development.
Collapse
Affiliation(s)
- Zhe Sang
- Department of Cell Biology, Pittsburgh, PA, USA
- Department Computational and Systems Biology, Pittsburgh, PA, USA
- University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA
| | - Yufei Xiang
- Department of Cell Biology, Pittsburgh, PA, USA
| | - Ivet Bahar
- Department Computational and Systems Biology, Pittsburgh, PA, USA
- University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA
| | - Yi Shi
- Department of Cell Biology, Pittsburgh, PA, USA
- University of Pittsburgh-Carnegie Mellon University Program in Computational Biology, Pittsburgh, PA, USA
| |
Collapse
|
14
|
Cho MK, Chong SH, Shin S, Ham S. Site-Specific Backbone and Side-Chain Contributions to Thermodynamic Stabilizing Forces of the WW Domain. J Phys Chem B 2021; 125:7108-7116. [PMID: 34165991 DOI: 10.1021/acs.jpcb.1c01725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The native structure of a protein is stabilized by a number of interactions such as main-chain hydrogen bonds and side-chain hydrophobic contacts. However, it has been challenging to determine how these interactions contribute to protein stability at single amino acid resolution. Here, we quantified site-specific thermodynamic stability at the molecular level to extend our understanding of the stabilizing forces in protein folding. We derived the free energy components of individual amino acid residues separately for the folding of the human Pin WW domain based on simulated structures. A further decomposition of the thermodynamic properties into contributions from backbone and side-chain groups enabled us to identify the critical residues in the secondary structure and hydrophobic core formation, without introducing physical modifications to the system as in site-directed mutagenesis methods. By relating the structural and thermodynamic changes upon folding for each residue, we find that the simultaneous formation of the backbone hydrogen bonds and side-chain contacts cooperatively stabilizes the folded structure. The identification of stabilizing interactions in a folding protein at atomic resolution will provide molecular insights into understanding the origin of the protein structure and into engineering a more stable protein.
Collapse
Affiliation(s)
- Myung Keun Cho
- Department of Chemistry, the Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa-ro 47-gil 100, Yongsan-ku, Seoul 04310, Korea.,Department of Chemistry, College of Natural Sciences, Seoul National University, Gwanak-ro 1, Gwanak-ku, Seoul 08826, Korea
| | - Song-Ho Chong
- Department of Chemistry, the Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa-ro 47-gil 100, Yongsan-ku, Seoul 04310, Korea
| | - Seokmin Shin
- Department of Chemistry, College of Natural Sciences, Seoul National University, Gwanak-ro 1, Gwanak-ku, Seoul 08826, Korea
| | - Sihyun Ham
- Department of Chemistry, the Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa-ro 47-gil 100, Yongsan-ku, Seoul 04310, Korea
| |
Collapse
|
15
|
Zhang M, Frederick TE, VanPelt J, Case DA, Peng JW. Coupled intra- and interdomain dynamics support domain cross-talk in Pin1. J Biol Chem 2020; 295:16585-16603. [PMID: 32963105 PMCID: PMC7864058 DOI: 10.1074/jbc.ra120.015849] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 09/19/2020] [Indexed: 11/06/2022] Open
Abstract
The functional mechanisms of multidomain proteins often exploit interdomain interactions, or "cross-talk." An example is human Pin1, an essential mitotic regulator consisting of a Trp-Trp (WW) domain flexibly tethered to a peptidyl-prolyl isomerase (PPIase) domain, resulting in interdomain interactions important for Pin1 function. Substrate binding to the WW domain alters its transient contacts with the PPIase domain via means that are only partially understood. Accordingly, we have investigated Pin1 interdomain interactions using NMR paramagnetic relaxation enhancement (PRE) and molecular dynamics (MD) simulations. The PREs show that apo-Pin1 samples interdomain contacts beyond the range suggested by previous structural studies. They further show that substrate binding to the WW domain simultaneously alters interdomain separation and the internal conformation of the WW domain. A 4.5-μs all-atom MD simulation of apo-Pin1 suggests that the fluctuations of interdomain distances are correlated with fluctuations of WW domain interresidue contacts involved in substrate binding. Thus, the interdomain/WW domain conformations sampled by apo-Pin1 may already include a range of conformations appropriate for binding Pin1's numerous substrates. The proposed coupling between intra-/interdomain conformational fluctuations is a consequence of the dynamic modular architecture of Pin1. Such modular architecture is common among cell-cycle proteins; thus, the WW-PPIase domain cross-talk mechanisms of Pin1 may be relevant for their mechanisms as well.
Collapse
Affiliation(s)
- Meiling Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Thomas E Frederick
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Jamie VanPelt
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - David A Case
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey, USA
| | - Jeffrey W Peng
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA.
| |
Collapse
|
16
|
Krupa P, Spodzieja M, Sieradzan AK. Prediction of CD28-CD86 protein complex structure using different level of resolution approach. J Mol Graph Model 2020; 103:107802. [PMID: 33246194 DOI: 10.1016/j.jmgm.2020.107802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/29/2020] [Accepted: 11/09/2020] [Indexed: 11/16/2022]
Abstract
Immune system plays essential role in functioning of higher organisms. Its hyperactivity can lead to autoimmune diseases or even anaphylactic shock while hypoactivity leads to proneness to infections or even cancer. T-cells play crucial role in immunity mechanisms and their activation and inhibition is strictly controlled by the regulatory proteins, such as CD28 and CTLA-4. Activity of these proteins is controlled by a pair of ligands, named CD80 and CD86, which can non-covalently bound to their receptors. While structure of human CTLA-4-CD86 complex in known, there is still no available structure for the CD28-CD86 system. To obtain the reliable structure of CD28-CD86 complex we first validated our methodology on the CTLA-4-CD86 system. Then coarse-grained UNRES-dock molecular docking simulation was performed followed by all-atom molecular dynamics simulations. As a result, we obtained a complete CD28-CD86 complex structure on atomistic level, in which interaction interface is consistent with available data. We also determined the kinetic properties for CTLA4-CD86 and CD28-CD86 complexes with use of coarse-grained model and determined the key residues for complex formation with use of Robetta, PPCheck and HawkDock servers. Our results not only verify high accuracy of the UNRES-dock method, but also provide a highly reliable model of the CD28-CD86 complex, which can be used in further studies and drug design.
Collapse
Affiliation(s)
- Paweł Krupa
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland; Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308, Gdańsk, Poland.
| | - Marta Spodzieja
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| | - Adam K Sieradzan
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308, Gdańsk, Poland
| |
Collapse
|
17
|
Westerlund AM, Fleetwood O, Pérez-Conesa S, Delemotte L. Network analysis reveals how lipids and other cofactors influence membrane protein allostery. J Chem Phys 2020; 153:141103. [DOI: 10.1063/5.0020974] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Annie M. Westerlund
- KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| | - Oliver Fleetwood
- KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| | - Sergio Pérez-Conesa
- KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| | - Lucie Delemotte
- KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| |
Collapse
|
18
|
Newaz K, Ghalehnovi M, Rahnama A, Antsaklis PJ, Milenković T. Network-based protein structural classification. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191461. [PMID: 32742675 PMCID: PMC7353965 DOI: 10.1098/rsos.191461] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
Experimental determination of protein function is resource-consuming. As an alternative, computational prediction of protein function has received attention. In this context, protein structural classification (PSC) can help, by allowing for determining structural classes of currently unclassified proteins based on their features, and then relying on the fact that proteins with similar structures have similar functions. Existing PSC approaches rely on sequence-based or direct three-dimensional (3D) structure-based protein features. By contrast, we first model 3D structures of proteins as protein structure networks (PSNs). Then, we use network-based features for PSC. We propose the use of graphlets, state-of-the-art features in many research areas of network science, in the task of PSC. Moreover, because graphlets can deal only with unweighted PSNs, and because accounting for edge weights when constructing PSNs could improve PSC accuracy, we also propose a deep learning framework that automatically learns network features from weighted PSNs. When evaluated on a large set of approximately 9400 CATH and approximately 12 800 SCOP protein domains (spanning 36 PSN sets), the best of our proposed approaches are superior to existing PSC approaches in terms of accuracy, with comparable running times. Our data and code are available at https://doi.org/10.5281/zenodo.3787922.
Collapse
Affiliation(s)
- Khalique Newaz
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
- Center for Network and Data Science, University of Notre Dame, Notre Dame, IN 46556, USA
- Eck institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Mahboobeh Ghalehnovi
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Arash Rahnama
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Panos J. Antsaklis
- Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Tijana Milenković
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
- Center for Network and Data Science, University of Notre Dame, Notre Dame, IN 46556, USA
- Eck institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
| |
Collapse
|
19
|
Mayol E, Campillo M, Cordomí A, Olivella M. Inter-residue interactions in alpha-helical transmembrane proteins. Bioinformatics 2019; 35:2578-2584. [PMID: 30566615 DOI: 10.1093/bioinformatics/bty978] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 10/19/2018] [Accepted: 12/17/2018] [Indexed: 01/23/2023] Open
Abstract
MOTIVATION The number of available membrane protein structures has markedly increased in the last years and, in parallel, the reliability of the methods to detect transmembrane (TM) segments. In the present report, we characterized inter-residue interactions in α-helical membrane proteins using a dataset of 3462 TM helices from 430 proteins. This is by far the largest analysis published to date. RESULTS Our analysis of residue-residue interactions in TM segments of membrane proteins shows that almost all interactions involve aliphatic residues and Phe. There is lack of polar-polar, polar-charged and charged-charged interactions except for those between Thr or Ser sidechains and the backbone carbonyl of aliphatic and Phe residues. The results are discussed in the context of the preferences of amino acids to be in the protein core or exposed to the lipid bilayer and to occupy specific positions along the TM segment. Comparison to datasets of β-barrel membrane proteins and of α-helical globular proteins unveils the specific patterns of interactions and residue composition characteristic of α-helical membrane proteins that are the clue to understanding their structure. AVAILABILITY AND IMPLEMENTATION Results data and datasets used are available at http://lmc.uab.cat/TMalphaDB/interactions.php. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
Collapse
Affiliation(s)
- Eduardo Mayol
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Mercedes Campillo
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Arnau Cordomí
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Mireia Olivella
- Bioinformatics Area, School of International Studies, ESCI-UPF, Barcelona, Spain.,Bioinformatics and Medical Statistics Group, U Science Tech, Central University of Catalonia, Vic, Barcelona, Spain
| |
Collapse
|
20
|
Hockenberry AJ, Wilke CO. Evolutionary couplings detect side-chain interactions. PeerJ 2019; 7:e7280. [PMID: 31328041 PMCID: PMC6622159 DOI: 10.7717/peerj.7280] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 06/09/2019] [Indexed: 12/19/2022] Open
Abstract
Patterns of amino acid covariation in large protein sequence alignments can inform the prediction of de novo protein structures, binding interfaces, and mutational effects. While algorithms that detect these so-called evolutionary couplings between residues have proven useful for practical applications, less is known about how and why these methods perform so well, and what insights into biological processes can be gained from their application. Evolutionary coupling algorithms are commonly benchmarked by comparison to true structural contacts derived from solved protein structures. However, the methods used to determine true structural contacts are not standardized and different definitions of structural contacts may have important consequences for interpreting the results from evolutionary coupling analyses and understanding their overall utility. Here, we show that evolutionary coupling analyses are significantly more likely to identify structural contacts between side-chain atoms than between backbone atoms. We use both simulations and empirical analyses to highlight that purely backbone-based definitions of true residue–residue contacts (i.e., based on the distance between Cα atoms) may underestimate the accuracy of evolutionary coupling algorithms by as much as 40% and that a commonly used reference point (Cβ atoms) underestimates the accuracy by 10–15%. These findings show that co-evolutionary outcomes differ according to which atoms participate in residue–residue interactions and suggest that accounting for different interaction types may lead to further improvements to contact-prediction methods.
Collapse
Affiliation(s)
- Adam J Hockenberry
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX, USA
| | - Claus O Wilke
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX, USA
| |
Collapse
|
21
|
Zhang M, Case DA, Peng JW. Propagated Perturbations from a Peripheral Mutation Show Interactions Supporting WW Domain Thermostability. Structure 2018; 26:1474-1485.e5. [PMID: 30197038 DOI: 10.1016/j.str.2018.07.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 06/21/2018] [Accepted: 07/25/2018] [Indexed: 12/18/2022]
Abstract
Inter-residue interactions stabilize protein folds and facilitate allosteric communication. Predicting which interactions are crucial and understanding why remain challenging. We highlight this through studies of a single peripheral mutation (Q33E) on the surface of the Pin1 WW domain that causes an unexpected loss of thermostability. Nuclear magnetic resonance studies attribute the loss to reorganizations of electrostatic and hydrophobic interactions, resulting in propagated conformational perturbations. The propagation demonstrates the cooperative response of Pin1 WW to external perturbations, consistent with its allosteric behavior within Pin1. Microsecond molecular dynamics simulations suggest the wild-type fold relies on couplings between a surface electrostatic network and a highly conserved hydrophobic core; Q33E directly perturbs the former, thereby disrupting the latter. These couplings suggest that predictions of mutation consequences that assume dominance of a single interaction type can be limiting, and highlight challenges in predicting protein mutational landscapes.
Collapse
Affiliation(s)
- Meiling Zhang
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN 46556, USA
| | - David A Case
- Department of Chemistry and Chemical Biology, Rutgers University, 174 Frelinghuysen Road, Piscataway, NJ 08854, USA
| | - Jeffrey W Peng
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN 46556, USA.
| |
Collapse
|
22
|
GRAFENE: Graphlet-based alignment-free network approach integrates 3D structural and sequence (residue order) data to improve protein structural comparison. Sci Rep 2017; 7:14890. [PMID: 29097661 PMCID: PMC5668259 DOI: 10.1038/s41598-017-14411-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 10/11/2017] [Indexed: 12/26/2022] Open
Abstract
Initial protein structural comparisons were sequence-based. Since amino acids that are distant in the sequence can be close in the 3-dimensional (3D) structure, 3D contact approaches can complement sequence approaches. Traditional 3D contact approaches study 3D structures directly and are alignment-based. Instead, 3D structures can be modeled as protein structure networks (PSNs). Then, network approaches can compare proteins by comparing their PSNs. These can be alignment-based or alignment-free. We focus on the latter. Existing network alignment-free approaches have drawbacks: 1) They rely on naive measures of network topology. 2) They are not robust to PSN size. They cannot integrate 3) multiple PSN measures or 4) PSN data with sequence data, although this could improve comparison because the different data types capture complementary aspects of the protein structure. We address this by: 1) exploiting well-established graphlet measures via a new network alignment-free approach, 2) introducing normalized graphlet measures to remove the bias of PSN size, 3) allowing for integrating multiple PSN measures, and 4) using ordered graphlets to combine the complementary PSN data and sequence (specifically, residue order) data. We compare synthetic networks and real-world PSNs more accurately and faster than existing network (alignment-free and alignment-based), 3D contact, or sequence approaches.
Collapse
|
23
|
Abstract
Allosteric effect implies ligand binding at one site leading to structural and/or dynamical changes at a distant site. PDZ domains are classic examples of dynamic allostery without conformational changes, where distal side-chain dynamics is modulated on ligand binding and the origin has been attributed to entropic effects. In this work, we unearth the energetic basis of the observed dynamic allostery in a PDZ3 domain protein using molecular dynamics simulations. We demonstrate that electrostatic interaction provides a highly sensitive yardstick to probe the allosteric modulation in contrast to the traditionally used structure-based parameters. There is a significant population shift in the hydrogen-bonded network and salt bridges involving side chains on ligand binding. The ligand creates a local energetic perturbation that propagates in the form of dominolike changes in interresidue interaction pattern. There are significant changes in the nature of specific interactions (nonpolar/polar) between interresidue contacts and accompanied side-chain reorientations that drive the major redistribution of energy. Interestingly, this internal redistribution and rewiring of side-chain interactions led to large cancellations resulting in small change in the overall enthalpy of the protein, thus making it difficult to detect experimentally. In contrast to the prevailing focus on the entropic or dynamic effects, we show that the internal redistribution and population shift in specific electrostatic interactions drive the allosteric modulation in the PDZ3 domain protein.
Collapse
|
24
|
Sequence statistics of tertiary structural motifs reflect protein stability. PLoS One 2017; 12:e0178272. [PMID: 28552940 PMCID: PMC5446159 DOI: 10.1371/journal.pone.0178272] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/10/2017] [Indexed: 11/19/2022] Open
Abstract
The Protein Data Bank (PDB) has been a key resource for learning general rules of sequence-structure relationships in proteins. Quantitative insights have been gained by defining geometric descriptors of structure (e.g., distances, dihedral angles, solvent exposure, etc.) and observing their distributions and sequence preferences. Here we argue that as the PDB continues to grow, it may become unnecessary to reduce structure into a set of elementary descriptors. Instead, it could be possible to deduce quantitative sequence-structure relationships in the context of precisely-defined complex structural motifs by mining the PDB for closely matching backbone geometries. To validate this idea, we turned to the the task of predicting changes in protein stability upon amino-acid substitution—a difficult problem of broad significance. We defined non-contiguous tertiary motifs (TERMs) around a protein site of interest and extracted sequence preferences from ensembles of closely-matching substructures in the PDB to predict mutational stability changes at the site, ΔΔGm. We demonstrate that these ensemble statistics predict ΔΔGm on par with state-of-the-art statistical and machine-learning methods on large thermodynamic datasets, and outperform these, along with a leading structure-based modeling approach, when tested in the context of unbiased diverse mutations. Further, we show that the performance of the TERM-based method is directly related to the amount of available relevant structural data, automatically improving with the growing PDB. This enables a means of estimating prediction accuracy. Our results clearly demonstrate that: 1) statistics of non-contiguous structural motifs in the PDB encode fundamental sequence-structure relationships related to protein thermodynamic stability, and 2) the PDB is now large enough that such statistics are already useful in practice, with their accuracy expected to continue increasing as the database grows. These observations suggest new ways of using structural data towards addressing problems of computational structural biology.
Collapse
|
25
|
HDInsight4PSi: Boosting performance of 3D protein structure similarity searching with HDInsight clusters in Microsoft Azure cloud. Inf Sci (N Y) 2016. [DOI: 10.1016/j.ins.2016.02.029] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
26
|
Terashi G, Takeda-Shitaka M. CAB-Align: A Flexible Protein Structure Alignment Method Based on the Residue-Residue Contact Area. PLoS One 2015; 10:e0141440. [PMID: 26502070 PMCID: PMC4621035 DOI: 10.1371/journal.pone.0141440] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 10/08/2015] [Indexed: 12/26/2022] Open
Abstract
Proteins are flexible, and this flexibility has an essential functional role. Flexibility can be observed in loop regions, rearrangements between secondary structure elements, and conformational changes between entire domains. However, most protein structure alignment methods treat protein structures as rigid bodies. Thus, these methods fail to identify the equivalences of residue pairs in regions with flexibility. In this study, we considered that the evolutionary relationship between proteins corresponds directly to the residue–residue physical contacts rather than the three-dimensional (3D) coordinates of proteins. Thus, we developed a new protein structure alignment method, contact area-based alignment (CAB-align), which uses the residue–residue contact area to identify regions of similarity. The main purpose of CAB-align is to identify homologous relationships at the residue level between related protein structures. The CAB-align procedure comprises two main steps: First, a rigid-body alignment method based on local and global 3D structure superposition is employed to generate a sufficient number of initial alignments. Then, iterative dynamic programming is executed to find the optimal alignment. We evaluated the performance and advantages of CAB-align based on four main points: (1) agreement with the gold standard alignment, (2) alignment quality based on an evolutionary relationship without 3D coordinate superposition, (3) consistency of the multiple alignments, and (4) classification agreement with the gold standard classification. Comparisons of CAB-align with other state-of-the-art protein structure alignment methods (TM-align, FATCAT, and DaliLite) using our benchmark dataset showed that CAB-align performed robustly in obtaining high-quality alignments and generating consistent multiple alignments with high coverage and accuracy rates, and it performed extremely well when discriminating between homologous and nonhomologous pairs of proteins in both single and multi-domain comparisons. The CAB-align software is freely available to academic users as stand-alone software at http://www.pharm.kitasato-u.ac.jp/bmd/bmd/Publications.html.
Collapse
Affiliation(s)
- Genki Terashi
- School of Pharmacy, Kitasato University, Tokyo, Japan
| | | |
Collapse
|
27
|
Kim H, Kihara D. Protein structure prediction using residue- and fragment-environment potentials in CASP11. Proteins 2015; 84 Suppl 1:105-17. [PMID: 26344195 DOI: 10.1002/prot.24920] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 08/03/2015] [Accepted: 08/31/2015] [Indexed: 11/08/2022]
Abstract
An accurate scoring function that can select near-native structure models from a pool of alternative models is key for successful protein structure prediction. For the critical assessment of techniques for protein structure prediction (CASP) 11, we have built a protocol of protein structure prediction that has novel coarse-grained scoring functions for selecting decoys as the heart of its pipeline. The score named PRESCO (Protein Residue Environment SCOre) developed recently by our group evaluates the native-likeness of local structural environment of residues in a structure decoy considering positions and the depth of side-chains of spatially neighboring residues. We also introduced a helix interaction potential as an additional scoring function for selecting decoys. The best models selected by PRESCO and the helix interaction potential underwent structure refinement, which includes side-chain modeling and relaxation with a short molecular dynamics simulation. Our protocol was successful, achieving the top rank in the free modeling category with a significant margin of the accumulated Z-score to the subsequent groups when the top 1 models were considered. Proteins 2016; 84(Suppl 1):105-117. © 2015 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Hyungrae Kim
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, 47906
| | - Daisuke Kihara
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, 47906. .,Department of Computer Science, Purdue University, West Lafayette, Indiana, 47907.
| |
Collapse
|
28
|
Abstract
Modularity is known as one of the most important features of protein's robust and efficient design. The architecture and topology of proteins play a vital role by providing necessary robust scaffolds to support organism's growth and survival in constant evolutionary pressure. These complex biomolecules can be represented by several layers of modular architecture, but it is pivotal to understand and explore the smallest biologically relevant structural component. In the present study, we have developed a component-based method, using protein's secondary structures and their arrangements (i.e. patterns) in order to investigate its structural space. Our result on all-alpha protein shows that the known structural space is highly populated with limited set of structural patterns. We have also noticed that these frequently observed structural patterns are present as modules or "building blocks" in large proteins (i.e. higher secondary structure content). From structural descriptor analysis, observed patterns are found to be within similar deviation; however, frequent patterns are found to be distinctly occurring in diverse functions e.g. in enzymatic classes and reactions. In this study, we are introducing a simple approach to explore protein structural space using combinatorial- and graph-based geometry methods, which can be used to describe modularity in protein structures. Moreover, analysis indicates that protein function seems to be the driving force that shapes the known structure space.
Collapse
Affiliation(s)
- Taushif Khan
- a School of Computational & Integrative Sciences , Jawaharlal Nehru University , New Delhi 110067 , India
| | - Indira Ghosh
- a School of Computational & Integrative Sciences , Jawaharlal Nehru University , New Delhi 110067 , India
| |
Collapse
|
29
|
Thompson JJ, Tabatabaei Ghomi H, Lill MA. Application of information theory to a three-body coarse-grained representation of proteins in the PDB: insights into the structural and evolutionary roles of residues in protein structure. Proteins 2014; 82:3450-65. [PMID: 25269778 DOI: 10.1002/prot.24698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/09/2014] [Accepted: 09/19/2014] [Indexed: 01/03/2023]
Abstract
Knowledge-based methods for analyzing protein structures, such as statistical potentials, primarily consider the distances between pairs of bodies (atoms or groups of atoms). Considerations of several bodies simultaneously are generally used to characterize bonded structural elements or those in close contact with each other, but historically do not consider atoms that are not in direct contact with each other. In this report, we introduce an information-theoretic method for detecting and quantifying distance-dependent through-space multibody relationships between the sidechains of three residues. The technique introduced is capable of producing convergent and consistent results when applied to a sufficiently large database of randomly chosen, experimentally solved protein structures. The results of our study can be shown to reproduce established physico-chemical properties of residues as well as more recently discovered properties and interactions. These results offer insight into the numerous roles that residues play in protein structure, as well as relationships between residue function, protein structure, and evolution. The techniques and insights presented in this work should be useful in the future development of novel knowledge-based tools for the evaluation of protein structure.
Collapse
Affiliation(s)
- Jared J Thompson
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, Indiana
| | | | | |
Collapse
|
30
|
Mary RD, Saravanan MK, Selvaraj S. Conservation of inter-residue interactions and prediction of folding rates of domain repeats. J Biomol Struct Dyn 2014; 33:534-51. [PMID: 24702623 DOI: 10.1080/07391102.2014.894944] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Domains are the main structural and functional units of larger proteins. They tend to be contiguous in primary structure and can fold and function independently. It has been observed that 10-20% of all encoded proteins contain duplicated domains and the average pairwise sequence identity between them is usually low. In the present study, we have analyzed the structural similarity between domain repeats of proteins with known structures available in the Protein Data Bank using structure-based inter-residue interaction measures such as the number of long-range contacts, surrounding hydrophobicity, and pairwise interaction energy. We used RADAR program for detecting the repeats in a protein sequence which were further validated using Pfam domain assignments. The sequence identity between the repeats in domains ranges from 20 to 40% and their secondary structural elements are well conserved. The number of long-range contacts, surrounding hydrophobicity calculations and pairwise interaction energy of the domain repeats clearly reveal the conservation of 3-D structure environment in the repeats of domains. The proportions of mainchain-mainchain hydrogen bonds and hydrophobic interactions are also highly conserved between the repeats. The present study has suggested that the computation of these structure-based parameters will give better clues about the tertiary environment of the repeats in domains. The folding rates of individual domains in the repeats predicted using the long-range order parameter indicate that the predicted folding rates correlate well with most of the experimentally observed folding rates for the analyzed independently folded domains.
Collapse
Affiliation(s)
- Rajathei David Mary
- a Department of Bioinformatics , School of Life Sciences, Bharathidasan University , Tiruchirappalli , Tamilnadu 620 024 , India
| | | | | |
Collapse
|
31
|
Koike R, Ota M, Kidera A. Hierarchical Description and Extensive Classification of Protein Structural Changes by Motion Tree. J Mol Biol 2014; 426:752-62. [DOI: 10.1016/j.jmb.2013.10.034] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/24/2013] [Accepted: 10/28/2013] [Indexed: 11/25/2022]
|
32
|
Mrozek D, Brożek M, Małysiak-Mrozek B. Parallel implementation of 3D protein structure similarity searches using a GPU and the CUDA. J Mol Model 2014; 20:2067. [PMID: 24481593 PMCID: PMC3936136 DOI: 10.1007/s00894-014-2067-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/11/2013] [Indexed: 01/16/2023]
Abstract
Searching for similar 3D protein structures is one of the primary processes employed in the field of structural bioinformatics. However, the computational complexity of this process means that it is constantly necessary to search for new methods that can perform such a process faster and more efficiently. Finding molecular substructures that complex protein structures have in common is still a challenging task, especially when entire databases containing tens or even hundreds of thousands of protein structures must be scanned. Graphics processing units (GPUs) and general purpose graphics processing units (GPGPUs) can perform many time-consuming and computationally demanding processes much more quickly than a classical CPU can. In this paper, we describe the GPU-based implementation of the CASSERT algorithm for 3D protein structure similarity searching. This algorithm is based on the two-phase alignment of protein structures when matching fragments of the compared proteins. The GPU (GeForce GTX 560Ti: 384 cores, 2GB RAM) implementation of CASSERT (“GPU-CASSERT”) parallelizes both alignment phases and yields an average 180-fold increase in speed over its CPU-based, single-core implementation on an Intel Xeon E5620 (2.40GHz, 4 cores). In this paper, we show that massive parallelization of the 3D structure similarity search process on many-core GPU devices can reduce the execution time of the process, allowing it to be performed in real time. GPU-CASSERT is available at: http://zti.polsl.pl/dmrozek/science/gpucassert/cassert.htm.
Collapse
Affiliation(s)
- Dariusz Mrozek
- Institute of Informatics, Silesian University of Technology, Gliwice, Poland,
| | | | | |
Collapse
|
33
|
Buck PM, Kumar S, Singh SK. On the role of aggregation prone regions in protein evolution, stability, and enzymatic catalysis: insights from diverse analyses. PLoS Comput Biol 2013; 9:e1003291. [PMID: 24146608 PMCID: PMC3798281 DOI: 10.1371/journal.pcbi.1003291] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 08/30/2013] [Indexed: 11/18/2022] Open
Abstract
The various roles that aggregation prone regions (APRs) are capable of playing in proteins are investigated here via comprehensive analyses of multiple non-redundant datasets containing randomly generated amino acid sequences, monomeric proteins, intrinsically disordered proteins (IDPs) and catalytic residues. Results from this study indicate that the aggregation propensities of monomeric protein sequences have been minimized compared to random sequences with uniform and natural amino acid compositions, as observed by a lower average aggregation propensity and fewer APRs that are shorter in length and more often punctuated by gate-keeper residues. However, evidence for evolutionary selective pressure to disrupt these sequence regions among homologous proteins is inconsistent. APRs are less conserved than average sequence identity among closely related homologues (≥80% sequence identity with a parent) but APRs are more conserved than average sequence identity among homologues that have at least 50% sequence identity with a parent. Structural analyses of APRs indicate that APRs are three times more likely to contain ordered versus disordered residues and that APRs frequently contribute more towards stabilizing proteins than equal length segments from the same protein. Catalytic residues and APRs were also found to be in structural contact significantly more often than expected by random chance. Our findings suggest that proteins have evolved by optimizing their risk of aggregation for cellular environments by both minimizing aggregation prone regions and by conserving those that are important for folding and function. In many cases, these sequence optimizations are insufficient to develop recombinant proteins into commercial products. Rational design strategies aimed at improving protein solubility for biotechnological purposes should carefully evaluate the contributions made by candidate APRs, targeted for disruption, towards protein structure and activity. Biotechnology requires the large-scale expression, yield, and storage of recombinant proteins. Each step in protein production has the potential to cause aggregation as proteins, not evolved to exist outside the cell, endure the various steps involved in commercial manufacturing processes. Mechanistic studies into protein aggregation have revealed that certain sequence regions contribute more to the aggregation propensity of a protein than other sequence regions do. Efforts to disrupt these regions have thus far indicated that rational sequence engineering is a useful technique to reduce the aggregation of biotechnologically relevant proteins. To improve our ability to rationally engineer proteins with enhanced expression, solubility, and shelf-life we conducted extensive analyses of aggregation prone regions (APRs) within protein sequences to characterize the various roles these regions play in proteins. Findings from this work indicate that protein sequences have evolved by minimizing their aggregation propensities. However, we also found that many APRs are conserved in protein families and are essential to maintain protein stability and function. Therefore, the contributions that APRs, targeted for disruption, make towards protein stability and function should be carefully evaluated when improving protein solubility via rational design.
Collapse
Affiliation(s)
- Patrick M Buck
- Pharmaceutical Research and Development, Biotherapeutics Pharmaceutical Sciences, Pfizer Inc., Chesterfield, Missouri, United States of America
| | | | | |
Collapse
|
34
|
Hleap JS, Susko E, Blouin C. Defining structural and evolutionary modules in proteins: a community detection approach to explore sub-domain architecture. BMC STRUCTURAL BIOLOGY 2013; 13:20. [PMID: 24131821 PMCID: PMC4016585 DOI: 10.1186/1472-6807-13-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 10/11/2013] [Indexed: 12/23/2022]
Abstract
Background Assessing protein modularity is important to understand protein evolution. Still the question of the existence of a sub-domain modular architecture remains. We propose a graph-theory approach with significance and power testing to identify modules in protein structures. In the first step, clusters are determined by optimizing the partition that maximizes the modularity score. Second, each cluster is tested for significance. Significant clusters are referred to as modules. Evolutionary modules are identified by analyzing homologous structures. Dynamic modules are inferred from sets of snapshots of molecular simulations. We present here a methodology to identify sub-domain architecture robustly, biologically meaningful, and statistically supported. Results The robustness of this new method is tested using simulated data with known modularity. Modules are correctly identified even when there is a low correlation between landmarks within a module. We also analyzed the evolutionary modularity of a data set of α-amylase catalytic domain homologs, and the dynamic modularity of the Niemann-Pick C1 (NPC1) protein N-terminal domain. The α-amylase contains an (α/β)8 barrel (TIM barrel) with the polysaccharides cleavage site and a calcium-binding domain. In this data set we identified four robust evolutionary modules, one of which forms the minimal functional TIM barrel topology. The NPC1 protein is involved in the intracellular lipid metabolism coordinating sterol trafficking. NPC1 N-terminus is the first luminal domain which binds to cholesterol and its oxygenated derivatives. Our inferred dynamic modules in the protein NPC1 are also shown to match functional components of the protein related to the NPC1 disease. Conclusions A domain compartmentalization can be found and described in correlation space. To our knowledge, there is no other method attempting to identify sub-domain architecture from the correlation among residues. Most attempts made focus on sequence motifs of protein-protein interactions, binding sites, or sequence conservancy. We were able to describe functional/structural sub-domain architecture related to key residues for starch cleavage, calcium, and chloride binding sites in the α-amylase, and sterol opening-defining modules and disease-related residues in the NPC1. We also described the evolutionary sub-domain architecture of the α-amylase catalytic domain, identifying the already reported minimum functional TIM barrel.
Collapse
Affiliation(s)
- Jose Sergio Hleap
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada.
| | | | | |
Collapse
|