Nakafuku M, Obara T, Kaibuchi K, Miyajima I, Miyajima A, Itoh H, Nakamura S, Arai K, Matsumoto K, Kaziro Y
Institute of Medical Science, University of Tokyo, Japan.
Proc Natl Acad Sci U S A. 1988 Mar;85(5):1374-8. doi: 10.1073/pnas.85.5.1374.
In a previous paper, we demonstrated that a gene coding for a protein homologous to the alpha subunit of mammalian guanine nucleotide-binding regulatory (G) proteins occurs in Saccharomyces cerevisiae. The gene, designated GPA1, encodes a protein (GP1 alpha) of 472 amino acids with a calculated Mr of 54,075. Here we report the isolation of another G-protein-homologous gene, GPA2, which encodes an amino acid sequence of 449 amino acid residues with a Mr of 50,516. The predicted primary structure of the GPA2-encoded protein (GP2 alpha) is homologous to mammalian G proteins [inhibitory and stimulatory G proteins (Gi and Gs, respectively), a G protein of unknown function (Go), and transducins (Gt)] as well as yeast GP1 alpha. When aligned with the alpha subunit of Gi (Gi alpha) to obtain maximal homology, GP2 alpha was found to contain a stretch of 83 additional amino acid residues near the NH2 terminus. The gene was mapped in chromosome V, close to the centromere. Haploid cells carrying a disrupted GPA2 gene are viable. Cells carrying a high copy number of plasmid GPA2 (YEpGPA2) had markedly elevated levels of cAMP and could suppress a temperature-sensitive mutation of RAS2. These results suggest that GPA2 may be involved in the regulation of cAMP levels in S. cerevisiae.
在之前的一篇论文中，我们证明酿酒酵母中存在一个编码与哺乳动物鸟嘌呤核苷酸结合调节（G）蛋白α亚基同源蛋白的基因。该基因命名为GPA1，编码一种由472个氨基酸组成的蛋白质（GP1α），计算所得的分子量为54,075。在此，我们报告另一个G蛋白同源基因GPA2的分离情况，它编码一个由449个氨基酸残基组成、分子量为50,516的氨基酸序列。GPA2编码的蛋白质（GP2α）的预测一级结构与哺乳动物G蛋白[抑制性和刺激性G蛋白（分别为Gi和Gs）、一种功能未知的G蛋白（Go）以及转导蛋白（Gt）]以及酵母GP1α同源。当与Gi的α亚基（Giα）比对以获得最大同源性时，发现GP2α在NH2末端附近含有一段额外的83个氨基酸残基。该基因定位于第五条染色体上，靠近着丝粒。携带破坏的GPA2基因的单倍体细胞是有活力的。携带高拷贝数质粒GPA2（YEpGPA2）的细胞中cAMP水平显著升高，并且能够抑制RAS2的温度敏感突变。这些结果表明，GPA2可能参与酿酒酵母中cAMP水平的调节。
