New insights into the mechanisms of SOS activation.
The activation of the small guanosine triphosphatase Ras is critical for many biological events. It is therefore not surprising that the ubiquitously expressed Ras guanine nucleotide exchange factor (GEF) SOS (Son of Sevenless), which couples protein tyrosine kinases to Ras activation, is under tight autoinhibitory control. Several studies have revealed how multiple regulatory domains might affect SOS activity. Most notably, a second Ras-binding site on SOS allosterically regulates the duration and amplitude of Ras activation. This allosteric Ras-GTP is produced by another GEF, Ras guanine nucleotide-releasing protein 1 (RasGRP1). SOS and RasGRP1 are both activated downstream of phospholipase D(2), and gain-of-function mutants of SOS contribute to inherited diseases. These studies not only enable us to better appreciate the complexity of the regulation of GEFs but also prompt us to reevaluate our current understanding of pathways that lead to Ras activation.
Quilliam
Lawrence A
LA
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, and Walther Cancer Institute, 635 Barnhill Drive, MS-4053, Indianapolis, IN 46202, USA. lquillia@iupui.edu
D000495:Allosteric Site; D000818:Animals; D020134:Catalytic Domain; D004268:DNA-Binding Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D011487:Protein Conformation; D020839:Son of Sevenless Protein, Drosophila / Q000737:chemistry / Q000378:metabolism*
D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; C491790:RASGRP1 protein, human; D020839:Son of Sevenless Protein, Drosophila