PreprintCited by 1,076Protein Structure and DynamicsMachine Learning in BioinformaticsEnzyme Structure and Function

The DOI matches its Crossref record; 71 of the 71 references it cites were found in a registry or an index; 19 of the 29 sources its claims cite were checked for support.

Improved prediction of protein-protein interactions using AlphaFold2

Open access
Bryant, P., Pozzati, G., Elofsson, A.·2021·Nature Communications

Preprint — published as 10.1038/s41467-022-28865-w · Paper page

Abstract

Predicting the structure of interacting protein chains is a fundamental step towards understanding protein function. Unfortunately, no computational method can produce accurate structures of protein complexes. AlphaFold2, has shown unprecedented levels of accuracy in modelling single chain protein structures. Here, we apply AlphaFold2 for the prediction of heterodimeric protein complexes. We find that the AlphaFold2 protocol together with optimized multiple sequence alignments, generate models with acceptable quality (DockQ≥0.23) for 63% of the dimers. From the predicted interfaces we create a simple function to predict the DockQ score which distinguishes acceptable from incorrect models as well as interacting from non-interacting proteins with state-of-art accuracy. We find that, using the predicted DockQ scores, we can identify 51% of all interacting pairs at 1% FPR. The protocol can be found at: https://gitlab.com/ElofssonLab/FoldDock .

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

AlphaFold2, combined with optimized paired MSAs, can fold-and-dock many heterodimeric protein complexes and predict model quality from the resulting interfaces. The derived pDockQ score separates acceptable from incorrect models and interacting from non-interacting proteins with state-of-art accuracy.

Key findings

  • On the test set, AF2 + paired MSAs reached a success rate of 57.8% (856/1481), rising to 61.7% when five seeds were ranked by pDockQ; block diagonalization + paired MSAs with top-ranked models reached 62.7%. The best development-set result was 39.4% for AF2 + paired MSAs.
  • pDockQ, a sigmoidal fit to interface pLDDT × log(interface contacts), predicted DockQ with an average error of 0.11 and separated acceptable models (DockQ ≥ 0.23) from incorrect ones with AUC 0.95; 31% of models were acceptable at 1% error and 54% at 10% error.
  • For interacting vs non-interacting proteins (1481 positives, 5694 negatives), pDockQ gave AUC 0.87 and identified 51% of interacting pairs at 1% FPR, compared with 27%, 18%, and 13% for interface pLDDT, interface contacts, and interface residues, respectively.
  • Performance varied by group: bacteria 73.7%, archaea 84.5%, eukarya 61%, virus 60%; E. coli 76.4%, S. cerevisiae 66.2%, H. sapiens 58.1%; helix interfaces 62%, sheet 59%, loop 53%; largest interface tertile 74% vs smallest 47%. AF2 outperformed tested docking methods, while AF-multimer reached 72.2% but was trained on the same data as the test set.

Methods

  • AF2 was used to model heterodimeric complexes with a chain break, no templates, and relaxation off. The development set contained 216 Dockground complexes; the test set contained 1481 complexes; additional sets included six CASP14 heterodimers, eight novel PDB complexes, and 5694 non-interacting pairs (3989 E. coli + 1705 mammalian).
  • MSA strategies compared default AF2 MSAs, organism-paired MSAs, block diagonalization MSAs, and combinations; AF2 model_1 vs model_1_ptm and different recycle/ensemble configurations were tested, with five seeds for the best strategy.
  • Models were assessed with DockQ (acceptable ≥ 0.23), ROC/AUC, and pDockQ; comparisons included RoseTTAFold, GRAMM, MDockPP, TMdock, and AF-multimer.

Limitations

  • Stated: only heterodimeric states are considered; alternative oligomeric states and larger biological assemblies are outside scope. Stated: interaction/non-interaction separation needs extension to compare interactions within individual organisms. Stated: the development vs test success-rate discrepancy (39.4% vs 57.8%) suggests unknown selection bias, and the development set is much smaller (216 vs 1481).
  • Evident: AF-multimer comparison is difficult because it was trained using the same data as the test set. Evident: the initial non-interacting set was only E. coli while positives were mainly eukaryotic, so the authors added mammalian negatives to obtain a more realistic estimate.
  • Evident: several analyses excluded complexes due to memory limits, MSA errors, missing Cβs, or DSSP failures (e.g., final test set 1481; DSSP 1391; RoseTTAFold 1455; AF-multimer 1458), which may affect generalizability.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1101/2021.09.15.460468

Cites

71 of 71 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

19 of 29 cited sources checked · 5 supported · 1 flagged · accuracy not yet measured

Show all 39 claims

  • It may state two separate claims as one. 38
  • Probably not a substantial claim. 36
  • The quote only partly states this claim. 1
62 of 62
  • The authors state this as an assumption.

    All residues in an interface contribute to the interaction energy.

    “Assuming that all residues in an interface contribute to the interaction energy could explain why larger interfaces are more likely to be correctly predicted.”
  • The paper relies on this without support.

    The 31% success rate at 1% FPR observed on the test set applies to the human reference interactome.

    “If 31% of these can be predicted at an error rate of 1%, this results in the structure of 19,842 human heterodimeric protein structures.”
  • The paper relies on this without support.

    The 3989 E. coli proteins used as negatives are truly non-interacting.

    “Using the best separator from the model ranking, the pDockQ, it is possible to distinguish the 3989 non-interacting proteins from Escherichia coli and the 1481 truly interacting proteins from the test set with an AUC of 0.87.”
  • The paper relies on this without support.

    The 1481 test set proteins used as positives are truly interacting.

    “Using the best separator from the model ranking, the pDockQ, it is possible to distinguish the 3989 non-interacting proteins from Escherichia coli and the 1481 truly interacting proteins from the test set with an AUC of 0.87.”
  • The paper relies on this without support.

    AF2 structure prediction is a non-deterministic process.

    “Since structure prediction with AF2 is a non-deterministic process, we generate five models initiated with different seeds.”
  • The paper relies on this without support.

    Ranking the five AF2 models for each complex by the number of residues in the interface gives the best result.

    “We rank the five models for each complex by the number of residues in the interface, giving the best result.”
6 of 6

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Two different average pDockQ errors for the test set

    Major

    The figure caption reports an overall average error of 0.14 DockQ, while the results text reports 0.11 for the same test set.

  • Model-ranking method conflicts with the reported ranking metric

    Minor

    The Methods say the five models are ranked by the number of interface residues, whereas the reported 61.7% success rate is attributed to ranking them by pDockQ. These are different metrics for selecting the top model.

  • Removing 65 homodimers does not leave 1705 complexes

    Minor

    Removing the stated 65 homodimers from 1964 complexes leaves 1899, not 1705; the text does not account for the other 194 removals.

    Reported 1705 · recomputed 1899

3 of 3

Citations

Cites

Flagged first, then by citations

Show all 66 references

Research works printed but not linked: 1

  1. 1997, Evaluation of GRAMM low-resolution docking methodology on the hemagglutinin-antibody complex, Proteins, Suppl 1, 226

Cited by

Sorted by citations

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Metadata

Authors
Bryant, P., Pozzati, G., & Elofsson, A.
Affiliations
Stockholm University (SE)
Corresponding author
  • Bryant, P.
  • Elofsson, A.
Venue
Nature Communications
Publisher
openRxiv
Published
2021-09-15
Volume
13
Issue
1
Pages
1265-1265
ISSN
2041-1723 (ISSN-L)
OpenAlex
W4220824576
Cited by
1,022
References
66
Citations by year
2026: 170 · 2025: 269 · 2024: 292 · 2023: 203 · 2022: 83 · 2021: 5
FWCI
62.72
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • Nature Communications (publishedVersion, cc-by)
  • Research Square (submittedVersion, cc-by)
  • bioRxiv (Cold Spring Harbor Laboratory) (submittedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • Swedish e-Science Research Centre
  • Knut och Alice Wallenbergs Stiftelse (COVID 19)
  • Vetenskapsrådet (2016-06301, Berzelius-2021-29)
  • Stockholms Universitet
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
protein-protein interaction, protein complex structure prediction, AlphaFold2, multiple sequence alignment, protein interface prediction
MeSH terms
Protein Conformation, Proteins, Computational Biology

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