期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 278, 期 5, 页码 3185-3196出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M207014200
关键词
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资金
- NCI NIH HHS [R01 CA72971] Funding Source: Medline
Activation of Raf-1 by Ras requires recruitment to the membrane as well as additional phosphorylations, including phosphorylation at serine 338 (Ser-338) and tyrosine 341 (Tyr-341). In this study we show that Tyr-341 participates in the recruitment of Raf-1 to specialized membrane domains called rafts, which are required for Raf-1 to be phosphorylated on Ser-338. Raf-1 is also thought to be recruited to the small G protein Rap1 upon GTP loading of Rap1. However, this does not result in Raf-1 activation. We propose that this is because Raf-1 is not phosphorylated on Tyr-341 upon recruitment to Rap1. Redirecting Rapl to Ras-containing membranes or mimicking Tyr-341 phosphorylation of Raf-1 by mutation converts Rapl into an activator of Raf-1. In contrast to Raf-1, B-Raf is activated by Rapl. We suggest that this is because B-Raf activation is independent of tyrosine phosphorylation. Moreover, mutants that render B-Raf dependent on tyrosine phosphorylation are no longer activated by Rap1.
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