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Exploring the alternative conformation of a known protein structure based on contact map prediction

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Li, Jiaxuan, Wang, Lei, Zhu, Zefeng, Song, Chen·2022·Journal of Chemical Information and Modeling

Preprint — published as 10.1021/acs.jcim.3c01381

Abstract

The rapid development of deep learning-based methods has considerably advanced the field of protein structure prediction. The accuracy of predicting the 3D structures of simple proteins is comparable to that of experimentally determined structures, providing broad possibilities for structure-based biological studies. Another critical question is whether and how multistate structures can be predicted from a given protein sequence. In this study, analysis of multiple two-state proteins demonstrated that deep learning-based contact map predictions contain structural information on both states, which suggests that it is probably appropriate to change the target of deep learningbased protein structure prediction from one specific structure to multiple likely structures. Furthermore, by combining deep learning- and physics-based computational methods, we developed a protocol for exploring alternative conformations from a known structure of a given protein, by which we successfully approached the holo-state conformation of a leucine-binding protein from its apo-state structure.

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Figures

Figure 1 Analysis of contacts in the PCMs for the additional 91 proteins. The number of apo-/holo-state-specific contacts (“101”/“011” in Table S1) were represented on the x/y axis. The size of the circles represented the proteins’ sequence length. Only medium- and long-range contacts are considered. The PCMs of 84 proteins cover certain amounts of the state-specific contacts of both states.
Figure 1 Analysis of contacts in the PCMs for the additional 91 proteins. The number of apo-/holo-state-specific contacts (“101”/“011” in Table S1) were represented on the x/y axis. The size of the circles represented the proteins’ sequence length. Only medium- and long-range contacts are considered. The PCMs of 84 proteins cover certain amounts of the state-specific contacts of both states.CC BY-NC-ND · PubMed Central
Figure 2 Workflow of our prediction method. We started with a known protein state structure and used the information extracted from its TCM and PCM to explore the alternative state structure.
Figure 2 Workflow of our prediction method. We started with a known protein state structure and used the information extracted from its TCM and PCM to explore the alternative state structure.CC BY-NC-ND · PubMed Central
Figure 3 Precision in the DCM prediction for the 91 two-state proteins. X-axis and y-axis represent the prediction precision before and after considering the flexibility of known protein structures, respectively. The precision was calculated as the number of true positives/number of all predicted positives.
Figure 3 Precision in the DCM prediction for the 91 two-state proteins. X-axis and y-axis represent the prediction precision before and after considering the flexibility of known protein structures, respectively. The precision was calculated as the number of true positives/number of all predicted positives.CC BY-NC-ND · PubMed Central
Figure 4 Extracting the likely contacts in the alternative conformation from the CM analysis, using LBP as an example. (A) Apo (blue, PDB ID: 1usg) and holo (gray, PDB ID: 1usi) structures of LBP showed a clear open–closed transition. (B) Comparison between the contact map from the holo state (TCM1, lower left) and the predicted contact map from its sequence (PCM, upper right) shows additional contacts of high prediction confidence (gray circle), which may represent new contacts in the alternative conformation. The star points are in correspondence with residue pairs in Table 3, where red stars represent residue pairs in bold and blue ones represent the rest. (C) The DCM is also shown for visualization. (D) Distances (in Å) between the four selected pairs of residues in the original apo-state structure, which were predicted to form contacts in the alternative state conformation.
Figure 4 Extracting the likely contacts in the alternative conformation from the CM analysis, using LBP as an example. (A) Apo (blue, PDB ID: 1usg) and holo (gray, PDB ID: 1usi) structures of LBP showed a clear open–closed transition. (B) Comparison between the contact map from the holo state (TCM1, lower left) and the predicted contact map from its sequence (PCM, upper right) shows additional contacts of high prediction confidence (gray circle), which may represent new contacts in the alternative conformation. The star points are in correspondence with residue pairs in Table 3, where red stars represent residue pairs in bold and blue ones represent the rest. (C) The DCM is also shown for visualization. (D) Distances (in Å) between the four selected pairs of residues in the original apo-state structure, which were predicted to form contacts in the alternative state conformation.CC BY-NC-ND · PubMed Central
Figure 5 Predicted contacts in the alternative state for the nine representative proteins. The residue pairs to form new contacts are linked with purple lines on the initial apo-state structures. Black arrows indicate the direction of conformational changes by inspecting the structures of both states.
Figure 5 Predicted contacts in the alternative state for the nine representative proteins. The residue pairs to form new contacts are linked with purple lines on the initial apo-state structures. Black arrows indicate the direction of conformational changes by inspecting the structures of both states.CC BY-NC-ND · PubMed Central
Figure 6 Modeling the alternative conformation of LBP with Rosetta. (A) Restraint energy function for the selected residue pairs during the optimization procedure. The initial distances between the four selected residue pairs are shown with cyan circles. (B) Scoring of the modeled structures and their RMSD with respect to the holo structure. 100 models were generated using Rosetta, and the RMSD between the apo and holo (target) states was indicated by dotted lines. The top 10 models (with the lowest scores) are represented in blue. The contact restraints were applied only on the four selected residue pairs. The correlation coefficient r between RMSD and energy score is labeled, too. (C) Best predicted conformation (yellow), overlapping with the closed-state structure (gray). The final distances between the selected residue pairs are shown in the enlarged view. (D) Similar to (B), but all 78 new contacts in the DCM were employed and restrained during the modeling.
Figure 6 Modeling the alternative conformation of LBP with Rosetta. (A) Restraint energy function for the selected residue pairs during the optimization procedure. The initial distances between the four selected residue pairs are shown with cyan circles. (B) Scoring of the modeled structures and their RMSD with respect to the holo structure. 100 models were generated using Rosetta, and the RMSD between the apo and holo (target) states was indicated by dotted lines. The top 10 models (with the lowest scores) are represented in blue. The contact restraints were applied only on the four selected residue pairs. The correlation coefficient r between RMSD and energy score is labeled, too. (C) Best predicted conformation (yellow), overlapping with the closed-state structure (gray). The final distances between the selected residue pairs are shown in the enlarged view. (D) Similar to (B), but all 78 new contacts in the DCM were employed and restrained during the modeling.CC BY-NC-ND · PubMed Central
Figure 7 Assessment of the modeled structures and their RMSD with respect to the target structures. Similar to Figure 6B, 100 models were generated for each protein with only the selected residue pairs subject to contact restraints. The RMSD between the apo and holo (target) states are indicated by dotted lines. The top 10 models (with the lowest scores) are represented in blue, while the worst 10 models (with the highest scores) were discarded. The remaining models are depicted in green. The fraction of the blue circles that are located to the left of the dashed lines is indicated in the upper left corner of each panel.
Figure 7 Assessment of the modeled structures and their RMSD with respect to the target structures. Similar to Figure 6B, 100 models were generated for each protein with only the selected residue pairs subject to contact restraints. The RMSD between the apo and holo (target) states are indicated by dotted lines. The top 10 models (with the lowest scores) are represented in blue, while the worst 10 models (with the highest scores) were discarded. The remaining models are depicted in green. The fraction of the blue circles that are located to the left of the dashed lines is indicated in the upper left corner of each panel.CC BY-NC-ND · PubMed Central
Figure 8 Comparison of the initial (blue), target (gray), and the best-modeled structures (yellow). The best-modeled structures represent the model with the lowest RMSD with respect to the target structure.
Figure 8 Comparison of the initial (blue), target (gray), and the best-modeled structures (yellow). The best-modeled structures represent the model with the lowest RMSD with respect to the target structure.CC BY-NC-ND · PubMed Central
Figure 9 Modeling the active conformation of rhodopsin from the predicted inactive structure by AlphaFold2. (A) The overlaid inactive crystal structure (blue, PDB ID: 2i35) and the predicted inactive structure by AlphaFold2 (pink). The RMSD between the two structures is 1.19 Å. (B) The predicted seven new contacts in the alternative state are indicated with purple lines on the AlphaFold2-predicted structure. (C) The best-sampled model in our prediction (yellow) successfully approached the active structure (gray, PDB ID: 6oy9) of rhodopsin, with an RMSD of 1.48 Å for helices 5 and 6. (D) Assessment of the 100 active-state models predicted using Rosetta and our protocol. The dashed line at 2.56 Å represents the RMSD between the AlphaFold2-predicted inactive model and active-state crystal structure (for helices 5 and 6).
Figure 9 Modeling the active conformation of rhodopsin from the predicted inactive structure by AlphaFold2. (A) The overlaid inactive crystal structure (blue, PDB ID: 2i35) and the predicted inactive structure by AlphaFold2 (pink). The RMSD between the two structures is 1.19 Å. (B) The predicted seven new contacts in the alternative state are indicated with purple lines on the AlphaFold2-predicted structure. (C) The best-sampled model in our prediction (yellow) successfully approached the active structure (gray, PDB ID: 6oy9) of rhodopsin, with an RMSD of 1.48 Å for helices 5 and 6. (D) Assessment of the 100 active-state models predicted using Rosetta and our protocol. The dashed line at 2.56 Å represents the RMSD between the AlphaFold2-predicted inactive model and active-state crystal structure (for helices 5 and 6).CC BY-NC-ND · PubMed Central

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Metadata

Authors
Li, J., Wang, L., Zhu, Z., & Song, C.
Affiliations
Peking University (CN)
Corresponding author
Song, Chen
Venue
Journal of Chemical Information and Modeling
Publisher
openRxiv
Published
2022-06-09
Volume
64
Issue
1
Pages
301-315
ISSN
1549-9596 (ISSN-L)
OpenAlex
W4389993920
Cited by
21
References
2
Citations by year
2026: 5 · 2025: 10 · 2024: 4 · 2023: 1 · 2022: 1
FWCI
1.78
Type
journal article
Language
en
Open access
Licence
cc-by-nc-nd
Locations
  • Journal of Chemical Information and Modeling (publishedVersion, cc-by-nc-nd)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
Funders
  • National Natural Science Foundation of China (21873006, 32071251)
  • Peking University
  • National Key Research and Development Program of China (2021YFE0108100)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Structure and Dynamics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Machine Learning in Bioinformatics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Structural Biology › Enzyme Structure and Function
Keywords
contact map prediction, two-state proteins, deep learning protein structure prediction, conformational change
MeSH terms
Amino Acid Sequence, Protein Conformation, Proteins, Computational Biology

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