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  • Title: Identification of amino acids in p21ras involved in exchange factor interaction.
    Author: Howe LR, Marshall CJ.
    Journal: Oncogene; 1993 Sep; 8(9):2583-90. PubMed ID: 8361768.
    Abstract:
    Through the genetic analysis of vulva development in C. elegans several different sites of mutation have been identified in the let-60 ras protein which have been postulated to affect the function of normal but not oncogenic p21ras (Beitel, G. J., S. G. Clark, and H. R. Horvitz. 1990. Nature 348: 503-509). We have introduced these mutations into mammalian Ha-ras and determined their effect on the function of cellular ras (c-ras), an oncogenically activated variant D12ras and the dominant negative N17ras. From these studies we conclude that two of the mutations S89-->F89 and delta 103-108 destabilise ras when it is in the GDP-bound form. However mutations at A66 and G75 lead to stable proteins on which a ras exchange factor SCD25 is unable to promote the formation of ras-GTP. The mutations at A66 show for the first time that helix alpha 2 of p21ras is involved in the stimulation of guanine nucleotide exchange by exchange factors.
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