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Yeast and mammalian ras proteins have conserved biochemical properties

G L Temeles, J B Gibbs, J S D'Alonzo

    Nature
    |February 21, 1985
    PubMed

    Insights

    Yeast ras proteins bind GTP and GDP, similar to mammalian ras proteins. Oncogenic mutations reduce GTP hydrolysis in both yeast and mammalian ras proteins, suggesting conserved functions.

    Area of Science:

    • Molecular Biology
    • Biochemistry
    • Genetics

    Background:

    • Mammalian ras oncogenes encode p21 proteins that bind GTP/GDP.
    • Oncogenic ras proteins have altered amino acids at specific positions (Gly 12, Ala 59, Gln 61).
    • Normal p21 proteins possess GTP hydrolytic activity, reduced by oncogenic substitutions.

    Purpose of the Study:

    • To investigate the biochemical functions of yeast ras-related proteins (SC1 and SC2).
    • To compare the GTP binding and hydrolytic activities of yeast ras proteins with mammalian counterparts.
    • To determine if oncogenic substitutions in yeast ras proteins affect GTP hydrolysis.

    Main Methods:

    • Sequence homology analysis between yeast and mammalian ras proteins.
    • GTP and GDP binding assays for yeast ras N-terminal domains.
    • GTPase activity assays for wild-type and mutant yeast ras proteins.

    Main Results:

    • Yeast RASsc1 and RASsc2 genes encode proteins homologous to mammalian p21.
    • The N-terminal domain of SC1 binds GTP and GDP.
    • Mutations analogous to mammalian oncogenic substitutions (SC1[Thr 66], SC1[Leu 68]) reduced GTP hydrolytic activity.

    Conclusions:

    • Yeast ras proteins share biochemical similarities with mammalian ras proteins.
    • GTP binding and hydrolysis are conserved functions across species.
    • Oncogenic substitutions impair GTPase activity in both yeast and mammalian ras proteins, implying conserved biological roles.

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