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Leveraging implicit knowledge in neural networks for functional dissection and engineering of proteins

Abstract

Proteins are nature’s most versatile molecular machines. Deep neural networks trained on large protein datasets have recently been used to tackle the unmet complexity of protein sequence–function relationships. The implicit knowledge contained in these networks represents a powerful, but thus far inaccessible, resource for understanding protein biology. Here, we show that occlusion-based sensitivity analysis can leverage the knowledge present in deep-neural-network-based protein sequence classifiers to identify functionally relevant parts of proteins. We first validated our approach by successfully predicting positions that mediate small molecule binding or catalytic activity across different protein classes. Next, we inferred the impact of point mutations on the activity of ERK and HRas, signalling factors frequently deregulated in cancer. Finally, we used our approach to identify engineering hotspots in CRISPR–Cas9 and anti-CRISPR protein AcrIIA4. Our work demonstrates how implicit knowledge in neural networks can be harnessed for protein functional dissection and protein engineering.

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Data availability

Sensitivity analysis data for all presented proteins, including the ~800 proteins used to calculate spatial homogeneity of sphere variances, as well as weights for DeeProtein classifier, are available on Zenodo (https://doi.org/10.5281/zenodo.2577920 and https://doi.org/10.5281/zenodo.2574979). AcrIIA4–LOV2 expression vectors can be obtained from the corresponding authors on reasonable request.

Code availability

The code for DeeProtein, including scripts employed for sensitivity analysis, and code for mapping sensitivities to protein 3D structures in PyMol, is available on GitHub under MIT License (https://github.com/juzb/DeeProtein, https://doi.org/10.5281/zenodo.2619339). A stand-alone compute capsule covering central functions of DeeProtein is available on Code Ocean (https://doi.org/10.24433/CO.1473214.v1)65.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Change history

  • 21 May 2019

    An amendment to this paper has been published and can be accessed via a link at the top of the paper

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Acknowledgements

This work was funded by the Klaus Tschira foundation, the German Research Foundation (DFG) and the Federal Ministry of Education and Research. We thank J. Quittek and M. Niepert (both at NEC), T. Wollmann (IPMB, BioQuant and the German Cancer Research Center (DKFZ)) for helpful discussions and M. Hemberger (BioQuant) for support with IT and GPU cluster use. J.U.z.B., T.B., S.H., L.A., C.G., M.K., J.M., P.P., L.P., M.P., M.S., D.H., M.D.H., M.J., C.S., M.W., I.L., D.N. and R.E. represent the iGEM Team Heidelberg 2017.

Author information

All members of the iGEM Team Heidelberg 2017 conceived the initial idea and J.U.z.B, T.B., S.H., I.L., D.N. and R.E. refined it. T.B., J.U.z.B. and S.H. implemented DeeProtein. J.U.z.B. performed sensitivity analysis. F.B. cloned AcrIIA4–LOV2 fusions and performed luciferase assays. J.U.z.B., T.B., S.H., F.B., D.N. and R.E. interpreted data. D.N. and R.E. jointly supervised the work. J.U.z.B., D.N. and R.E. wrote the paper with support from T.B. and S.H. All authors approved the manuscript.

Competing interests

F.B., M.D.H., D.N. and R.E. have filed a European Patent application (17196813.4) for the AcrIIA4–LOV2 constructs.

Correspondence to Dominik Niopek or Roland Eils.

Supplementary information

Supplementary Information

Supplementary Figs. 1–10, Supplementary Tables 3–6, Supplementary Notes 1–4, Supplementary references,

Reporting Summary

Supplementary Table 1

Ligand binding sensitivity

Supplementary Table 2

Sensitivity for catalytic activity

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Fig. 1: Sensitivity analysis pipeline for functional annotation and engineering of proteins.
Fig. 2: DeeProtein architecture and performance evaluation.
Fig. 3: Sensitivity analysis highlights ligand binding regions and active sites.
Fig. 4: Sensitivity analysis infers catalytic residues in kinases.
Fig. 5: ERK2 sensitivity analysis dissects functional regions and identifies mutation-intolerant residues.
Fig. 6: CRISPR–Cas9 nuclease sensitivity can infer the biological activity of CRISPR–Cas9 domain insertion mutants.
Fig. 7: Sensitivity analysis can infer an engineering hotspot in anti-CRISPR protein AcrIIA4.