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In Vivo Functional Analysis of the Ras Exchange Factor Son of Sevenless

1995; American Association for the Advancement of Science; Volume: 268; Issue: 5210 Linguagem: Inglês

10.1126/science.7725106

1095-9203

Chris Karlovich, Laura Bonfini, Linda McCollam, Ronald D. Rogge, Andrea Daga, Michael Czech, Utpal Banerjee,

Phagocytosis and Immune Regulation

The Son of sevenless (Sos) protein functions as a guanine nucleotide transfer factor for Ras and interacts with the receptor tyrosine kinase Sevenless through the protein Drk, a homolog of mammalian Grb2. In vivo structure-function analysis revealed that the amino terminus of Sos was essential for its function in flies. A molecule lacking the amino terminus was a potent dominant negative. In contrast, a Sos fragment lacking the Drk binding sites was functional and its activity was dependent on the presence of the Sevenless receptor. Furthermore, membrane localization of Sos was independent of Drk. A possible role for Drk as an activator of Sos is discussed and a Drk-independent interaction between Sos and Sevenless is proposed that is likely mediated by the pleckstrin homology domain within the amino terminus.