Tanaka K, Nakafuku M, Satoh T, Marshall M S, Gibbs J B, Matsumoto K, Kaziro Y, Toh-e A
Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan.
Cell. 1990 Mar 9;60(5):803-7. doi: 10.1016/0092-8674(90)90094-u.
The IRA1 and IRA2 genes of S. cerevisiae encode closely related proteins that also share homology with mammalian GAP (ras GTPase activating protein). The RAS1 and RAS2 proteins overexpressed in ira mutants accumulated in the GTP-bound form, whereas in the wild-type strain the proteins were found mostly in the GDP-bound form, indicating that IRA1 and IRA2 negatively regulate the level of RAS-GTP. In contrast, the RAS2Val-19 or RAS2Thr-66 mutant protein was bound to GTP in high amounts irrespective of the IRA genotype. Overexpression of bovine GAP suppressed the phenotypes of ira mutants by reducing the level of RAS-GTP, suggesting that IRA proteins may be functionally analogous to mammalian GAP.
酿酒酵母的IRA1和IRA2基因编码密切相关的蛋白质，这些蛋白质也与哺乳动物的GAP（ras GTP酶激活蛋白）具有同源性。在ira突变体中过表达的RAS1和RAS2蛋白以GTP结合形式积累，而在野生型菌株中，这些蛋白大多以GDP结合形式存在，这表明IRA1和IRA2负向调节RAS-GTP的水平。相比之下，无论IRA基因型如何，RAS2Val-19或RAS2Thr-66突变蛋白都大量结合GTP。牛GAP的过表达通过降低RAS-GTP水平抑制了ira突变体的表型，这表明IRA蛋白在功能上可能类似于哺乳动物的GAP。
