Visualizations of biomolecular structures empower us to gain insights into biological functions, generate testable hypotheses, and communicate biological concepts. Typical visualizations (such as ball and stick) primarily depict covalent bonds. In contrast, non-covalent contacts between atoms, which govern normal physiology, pathogenesis, and drug action, are seldom visualized. We present the Protein Contacts Atlas, an interactive resource of non-covalent contacts from over 100,000 PDB crystal structures. We developed multiple representations for visualization and analysis of non-covalent contacts at different scales of organization: atoms, residues, secondary structure, subunits, and entire complexes. The Protein Contacts Atlas enables researchers from different disciplines to investigate diverse questions in the framework of non-covalent contacts, including the interpretation of allostery, disease mutations and polymorphisms, by exploring individual subunits, interfaces, and protein–ligand contacts and by mapping external information. The Protein Contacts Atlas is available at http://www.mrc-lmb.cam.ac.uk/pca/ and also through PDBe.

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We thank A. Lesk, C. Chothia, S. Balaji, H. Harbrecht, I. Huppertz, M. Ouédraogo, G. Chalancon, A. Morgunov, A. Murzin, A. Andreeva, G. de Baets, R. Peer, S. Chavali, A. Sente, N. S. Latysheva, A. Gunnarsson, and A. Hauser for their comments on this work. We thank T. Nakane for his inputs on structure visualization using WebGLMol. This work was supported by the Medical Research Council (MC_U105185859; M.M.B., M.K., C.N.J.R., T.F., A.J.V., and J.S.-B.), the LMB-Cambridge scholarship (A.J.V.), the St. John's College Benefactor scholarship (A.J.V.), the AFR scholarship from the Luxembourg National Research Fund (C.N.J.R.), and the Boehringer Ingelheim Fond (T.F.). T.F. is a Research Fellow of Fitzwilliam College, University of Cambridge, UK. M.M.B. is a Lister Institute Research Prize Fellow.

Author information

Author notes

    • Melis Kayikci

    Present address: Genomics England, London, UK

    • A. J. Venkatakrishnan

    Present address: Department of Molecular and Cellular Physiology, Department of Computer Science, and Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA

    • James Scott-Brown

    Present address: University of Oxford, Oxford, UK

    • Tilman Flock

    Present address: Paul Scherrer Institute, Villigen, Switzerland

  1. Melis Kayikci and A.J. Venkatakrishnan contributed equally to this work.


  1. MRC Laboratory of Molecular Biology, Cambridge, UK

    • Melis Kayikci
    • , A. J. Venkatakrishnan
    • , James Scott-Brown
    • , Charles N. J. Ravarani
    • , Tilman Flock
    •  & M. Madan Babu
  2. Fitzwilliam College, University of Cambridge, Cambridge, UK

    • Tilman Flock


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M.K. collected the data, developed the computational pipeline, and built the web server. A.J.V. designed the prototype of the representations with M.M.B. A.J.V., M.K., J.S.-B., and M.M.B. optimized the representations, and M.K. and J.S.-B. implemented the representations. M.K. and A.J.V. performed the GPCR analyses. J.S.-B. made the prototype of the web server. C.N.J.R. and T.F. helped with the web server and analyzing examples. M.K., C.N.J.R., and A.J.V. independently wrote separate drafts of the manuscript. M.K., A.J.V., and M.M.B. wrote the final manuscript with critical inputs from C.N.J.R., J.S.-B., and T.F.; M.K., A.J.V., and C.N.J.R. prepared the figures. A.J.V. and M.M.B. conceived and planned the project. M.K., A.J.V., and M.M.B. executed the project. M.M.B. supervised the project.

Competing interests

The authors declare no competing financial interest.

Corresponding authors

Correspondence to Melis Kayikci or A. J. Venkatakrishnan or M. Madan Babu.

Integrated supplementary information

  1. Supplementary Figure 1 Plot of all PDB structures analyzed

    a, The number of residues (x-axis) vs the number of non-covalent residue contacts (y-axis) in each PDB. b, The number of atoms (x-axis) vs the number of non-covalent atomic contacts (y-axis) in each PDB. Each dot represents a PDB structure. On average, each of these structures contains 5,677 atoms, 45,042 atomic contacts, 684 residues, 3,043 residue contacts, 3 chains, 2,441 atomic contacts between chains, and 125 residue contacts between chains.

  2. Supplementary Figure 2 Visualization and analysis page

    The biomolecular complex network panel, sequence panel, 3D structure panel and contacts panel are shown for the β2 adrenergic receptor-G protein complex structure (PDB ID: 3SN6). The sequence panel shows the secondary structure elements (SSEs) and the amino acid sequence. In the sequence panel, some positions are highlighted with a line on the top, using bold typeface or a red color. A line on top of a residue denotes availability of disease mutation data via Uniprot, which can be accessed by moving the mouse over the residue. Bold letters denote residues that were previously hovered over. Red colored letters denote residues currently selected. Helices are represented as rectangles and sheets are represented by arrows. The top line shows the entire SSEs of the chain and the line below shows the zoomed in version with the loops as a thin black line. The size of the rectangles and arrows are proportional to the length of the SSEs. The contacts panel shows the secondary structures view in which the chord plot can be seen on the top left corner with the selected secondary structures (Helix 38 in blue and Helix 40 in orange). In the middle, the residue contact matrix is shown with all the contacting residues of the selected SSEs. The residues belonging to each SSE are highlighted in their respective colors. The number of atomic contacts is shown within the matrix. On the right is the 3D structure panel, which shows the 3D view of the receptor (grey cartoon view).

  3. Supplementary Figure 3 Mapping disease mutations in rhodopsin

    a, Selected residues of rhodopsin (1GZM; shown in the text field) are highlighted on the scatter plot in red. b, 3D structure view of rhodopsin (1GZM, chain A) is shown in network view (grey) with contacts highlighted in blue. The thickness of the residue contact denotes the number of atomic contacts made by the interacting residues.

  4. Supplementary Figure 4 Mapping external information for residue-level analysis of structures

    a, Scatter plot of residues in the G protein after mapping their stability data (experimentally inferred binding affinity) using a color spectrum (min: cyan; max: magenta). Stability was measured as ΔTm = Tm of Gαi1(Ala) - Tm of Gαi1(WT) with 1mM GDP. Residue F336G.H5.8 is shown in red and the rest of the residues in cyan and magenta according to their ΔTm values. b, Network view and asteroid plot of F336G.H5.8 shows the extensive nature of the contacts this residue mediates in the GDP bound structure of Gαi1 (1GDD).

  5. Supplementary Figure 5 Average of the maximum number of atomic contacts made by a residue across all non-redundant crystal structures

    These values are used to normalize the contacts with respect to the size of the amino acid (Methods).

Supplementary information

  1. Supplementary Text and Figures

    Supplementary Figures 1–5 and Supplementary Notes 1 and 2

  2. Life Sciences Reporting Summary

  3. Supplementary Data Set 1

    Sample downloadable statistics for PDB 3SN6.

  4. Supplementary Data Set 2

    Sample downloadable list of contacts for PDB 3SN6.

  5. Supplementary Data Set 3

    Sample downloadable structure report for PDB 5C1M.

  6. Supplementary Data Set 4

    Raw data used for analysis of Rhodopsin conformational cycle.

  7. Supplementary Data Set 5

    Contact statistics for all structures in the PDB.

  8. Supplementary Data Set 6

    Source Data, Supplementary Fig. 5a,d.

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