The Saccharomyces cerevisiae Rheb G-protein Is Involved in Regulating Canavanine Resistance and Arginine Uptake*
The Saccharomyces cerevisiae Rheb G-protein Is Involved in Regulating Canavanine Resistance and Arginine Uptake*
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DOI：
10.1074/jbc.275.15.11198
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发表时间：
2000-04
期刊：
影响因子：
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通讯作者：
J. Urano;A. P. Tabancay;Wenli Yang;F. Tamanoi
中科院分区：
文献类型：
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作者：
J. Urano;A. P. Tabancay;Wenli Yang;F. Tamanoi
G蛋白Ras超家族的新成员Rheb已在大鼠和人类中被鉴定，但其功能尚未确定。我们在这里报告的Rheb同系物的芽殖酵母酿酒酵母（ScRheb）以及裂殖酵母，果蝇，斑马鱼，和玻璃海鞘。这些蛋白质基于1）它们的总体序列相似性，2）它们的效应子结构域序列的高度保守性，3）它们的G1盒中存在独特的精氨酸，和4）存在保守的CAAX法尼基化基序，定义了一类新的G蛋白。一个S. ScRheb缺陷的酿酒酵母菌株显示其对刀豆氨酸和硫代赖氨酸的生长抑制作用过敏，刀豆氨酸和硫代赖氨酸分别是精氨酸和赖氨酸的类似物。因此，精氨酸和赖氨酸的摄取在ScRheb缺陷型菌株中增加。这种增加的精氨酸摄取需要精氨酸特异性通透酶Can 1 p。ScRheb的功能依赖于具有完整的效应子结构域，因为ScRheb的效应子结构域中的突变不能补充ScRheb破坏细胞的刀豆氨酸超敏性。此外，G1盒中的保守精氨酸在ScRheb的活性中起作用，因为该精氨酸突变为甘氨酸显著降低了ScRheb补充ScRheb缺陷型酵母的刀豆氨酸超敏反应的能力。最后，C-末端CAAX法尼基化基序的突变导致ScRheb功能丧失。这一结果，结合我们发现ScRheb是法尼基化的，表明法尼基化在ScRheb功能中起着关键作用。我们的研究结果分配的精氨酸和赖氨酸摄取的调节作为这个新的法尼基化的Ras超家族G蛋白的第一个生理功能。
The new member of the Ras superfamily of G-proteins, Rheb, has been identified in rat and human, but its function has not been defined. We report here the identification of Rheb homologues in the budding yeast Saccharomyces cerevisiae (ScRheb) as well as in Schizosaccharomyces pombe, Drosophila melanogaster, zebrafish, andCiona intestinalis. These proteins define a new class of G-proteins based on 1) their overall sequence similarity, 2) high conservation of their effector domain sequence, 3) presence of a unique arginine in their G1 box, and 4) presence of a conserved CAAX farnesylation motif. Characterization of an S. cerevisiae strain deficient in ScRheb showed that it is hypersensitive to growth inhibitory effects of canavanine and thialysine, which are analogues of arginine and lysine, respectively. Accordingly, the uptake of arginine and lysine was increased in the ScRheb-deficient strain. This increased arginine uptake requires the arginine-specific permease Can1p. The function of ScRheb is dependent on having an intact effector domain since mutations in the effector domain of ScRheb are incapable of complementing canavanine hypersensitivity of scrheb disruptant cells. Furthermore, the conserved arginine in the G1 box plays a role in the activity of ScRheb, as a mutation of this arginine to glycine significantly reduced the ability of ScRheb to complement canavanine hypersensitivity of ScRheb-deficient yeast. Finally, a mutation in the C-terminal CAAX farnesylation motif resulted in a loss of ScRheb function. This result, in combination with our finding that ScRheb is farnesylated, suggests that farnesylation plays a key role in ScRheb function. Our findings assign the regulation of arginine and lysine uptake as the first physiological function for this new farnesylated Ras superfamily G-protein.