ras effector loop mutations that dissociate p120GAP and neurofibromin interactions

✍ Scribed by Stacey Stang; Drell Bottorff; James C. Stone

• Book ID: 102656953
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 626 KB
• Volume: 15
• Category: Article
• ISSN: 0899-1987
• DOI: 10.1002/(sici)1098-2744(199601)15:1<64::aid-mc9>3.0.co;2-s

✦ Synopsis

ras proteins are positively regulated by nucleotide exchange factors and negatively regulated by GTPaseactivating proteins (GAPs). Two GAPs have been found in mammalian cells, pl2OGAP and neurofibromin, the product of the type 1 neurofibromatosis (NF7) gene. A library of substitutions in the effector loop region of ras in an Escherichia coli plasmid expression system was screened for c-Ha-ras species with altered GAP interactions. Several substitutions preferentially disrupted t h e interaction of ras with pl 2OGAP as compared with the interaction with the recombinant GAP-related domain of neurofibromin (NF1-GRD). The most extreme example, Tyr32His, encoded a ras species that was unaffected by pl2OGAP but was stimulated normally by NFI-GRD. Tyr32His was weakly transforming in Rat2 cells. Tyr32His ras was primarily GDP-bound in quiescent Rat2 cells, although it rapidly associated with GTP after treatment of cells with epidermal growth factor. These results show that t h e NF1 product has less stringent requirements than pl2OGAP for ras effector domain structure and that negative regulation of ras can be achieved in rat fibroblasts by the product of NF7.