Phosphorylation of the Kinase Suppressor of Ras by Associated Kinases

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• 作者：Deanna J. Volle ; Jennifer A. Fulton ; Oleg V. Chaika ; Kim McDermott ; Han Huang ; Laurey A. Steinke ; and Robert E. Lewis
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：April 20, 1999
• 年：1999
• 卷：38
• 期：16
• 页码：5130 - 5137
• 全文大小：157K
• 年卷期：v.38,no.16(April 20, 1999)
• ISSN：1520-4995

文摘

The kinase suppressor of Ras (KSR) is a loss-of-function allele that suppresses the rough eyephenotype of activated Ras in Drosophila and the multivulval phenotype of activated Ras in Caenorhabditiselegans. The physiological role of mammalian KSR is not known. We examined the mechanisms regulatingthe phosphorylation of this putative kinase in mammalian cells. Wild-type mouse KSR and a mutatedKSR protein predicted to create a kinase-dead protein are phosphorylated identically in intact cells and inthe immune complex. Phosphopeptide sequencing identified 10 in vivo phosphorylation sites in KSR, allof which reside in the 539 noncatalytic amino terminal amino acids. Expression of the amino terminalportion of KSR alone demonstrated that it was phosphorylated in the intact cell and in an immune complexin a manner indistinguishable from that of intact KSR. These data demonstrate that the kinase domain ofKSR is irrelevant to its phosphorylation state and suggest that the phosphorylation of KSR and its associationwith a distinct set of kinases may affect intracellular signaling.