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Science. 2019 Mar 8;363(6431):1098-1103. doi: 10.1126/science.aau5721. Epub 2019 Mar 7.

A molecular assembly phase transition and kinetic proofreading modulate Ras activation by SOS.

Author information

1
Department of Chemistry, University of California, Berkeley, CA 94720, USA.
2
Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA.
3
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
4
California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA.
5
Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
6
Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA.
7
Divisions of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
8
Department of Chemistry, University of California, Berkeley, CA 94720, USA. jtgroves@lbl.gov.
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Contributed equally

Abstract

The guanine nucleotide exchange factor (GEF) Son of Sevenless (SOS) is a key Ras activator that is autoinhibited in the cytosol and activates upon membrane recruitment. Autoinhibition release involves structural rearrangements of the protein at the membrane and thus introduces a delay between initial recruitment and activation. In this study, we designed a single-molecule assay to resolve the time between initial receptor-mediated membrane recruitment and the initiation of GEF activity of individual SOS molecules on microarrays of Ras-functionalized supported membranes. The rise-and-fall shape of the measured SOS activation time distribution and the long mean time scale to activation (~50 seconds) establish a basis for kinetic proofreading in the receptor-mediated activation of Ras. We further demonstrate that this kinetic proofreading is modulated by the LAT (linker for activation of T cells)-Grb2-SOS phosphotyrosine-driven phase transition at the membrane.

PMID:
30846600
DOI:
10.1126/science.aau5721

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