Ras proteins are highly conserved signaling molecules that exhibit regulated, nucleotide-dependent switching between active and inactive states. The high conservation of Ras requires mechanistic explanation, especially given the general mutational to ...
Ras proteins are highly conserved signaling molecules that exhibit regulated, nucleotide-dependent switching between active and inactive states. The high conservation of Ras requires mechanistic explanation, especially given the general mutational tolerance of proteins. Here, we use deep mutational scanning, biochemical analysis and molecular simulations to understand constraints on Ras sequence. Ras exhibits global sensitivity to mutation when regulated by a GTPase activating protein and a nucleotide exchange factor. Removing the regulators shifts the distribution of mutational effects to be largely neutral, and reveals hotspots of activating mutations in residues that restrain Ras dynamics and promote the inactive state. Evolutionary analysis, combined with structural and mutational data, argue that Ras has co-evolved with its regulators in the vertebrate lineage. Overall, our results show that sequence conservation in Ras depends strongly on the biochemical network in which it operates, providing a framework for understanding the origin of global selection pressures on proteins.
Organizational Affiliation:
California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States.,Department of Bioengineering and Therapeutic Sciences, California Institute for Quantitative Biomedical Research, University of California, San Francisco, San Francisco, United States.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, United States.,Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, United States.,Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, United States.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, United States.,Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Ragon Institute of MGH, MIT and Harvard, Cambridge, United States.,Department of Physics, Massachusetts Institute of Technology, Cambridge, United States.
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