Uncovering the basis of protein-protein interaction specificity with a combinatorially complete library
- Massachusetts Institute of Technology, United States
Abstract
Protein-protein interaction specificity is often encoded at the primary sequence level. However, the contributions of individual residues to specificity are usually poorly understood and often obscured by mutational robustness, sequence degeneracy, and epistasis. Using bacterial toxin-antitoxin systems as a model, we screened a combinatorially complete library of antitoxin variants at three key positions against two toxins. This library enabled us to measure the effect of individual substitutions on specificity in hundreds of genetic backgrounds. These distributions allow inferences about the general nature of interface residues in promoting specificity. We find that positive and negative contributions to specificity are neither inherently coupled nor mutually exclusive. Further, a wild-type antitoxin appears optimized for specificity as no substitutions improve discrimination between cognate and non-cognate partners. By comparing crystal structures of paralogous complexes, we provide a rationale for our observations. Collectively, this work provides a generalizable approach to understanding the logic of molecular recognition.
Data availability
Diffraction data have been deposited in PDB under the accession code 6X0A. Datasets generated during this study have been deposited in GEO. Raw data, variant frequency, and variant fitness scores can be found under the accession number GSE153897.
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The genetic landscape of protein-protein interaction specificityNCBI Gene Expression Omnibus, GSE153897.
Article and author information
Author details
Funding
National Institutes of Health (T32GM007753)
- Thuy-Lan V Lite
Howard Hughes Medical Institute
- Michael T Laub
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Lite et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Uncovering the basis of protein-protein interaction specificity with a combinatorially complete library
eLife 9:e60924.
https://doi.org/10.7554/eLife.60924
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