Itoh H, Kozasa T, Nagata S, Nakamura S, Katada T, Ui M, Iwai S, Ohtsuka E, Kawasaki H, Suzuki K
Proc Natl Acad Sci U S A. 1986 Jun;83(11):3776-80. doi: 10.1073/pnas.83.11.3776.
We have cloned cDNAs encoding alpha subunits of the guanine nucleotide-binding proteins Gs, Gi, and Go and determined their nucleotide sequences. Purified preparations of Gi and Go alpha subunits (Gi alpha and Go alpha) from rat brain were completely digested with trypsin, and peptides were subjected to amino acid sequence analysis. By screening of a cDNA library from rat C6 glioma cells with a synthetic probe corresponding to a 17 amino acid sequence, a clone encoding the sequence of Go alpha was obtained. Then, the library was rescreened with a Go alpha cDNA probe to isolate several strongly or weakly hybridizing clones. cDNAs encoding the complete sequences of Gi alpha and Gs alpha were thus obtained. From nucleotide sequence analysis, the amino acid sequences of Gs alpha and Gi alpha were deduced; they contain 394 and 355 amino acid residues (including the initiator methionine), respectively. The calculated molecular weights for Gs alpha and Gi alpha were 45,663 and 40,499, respectively. The Go alpha clone encoded a sequence of 310 amino acid residues that lacked the NH2 terminus. The homology of the alpha subunits of Gs, Gi, Go, transducin, and ras-encoded protein is discussed.
我们已经克隆了编码鸟嘌呤核苷酸结合蛋白Gs、Gi和Go的α亚基的cDNA，并确定了它们的核苷酸序列。用胰蛋白酶完全消化从大鼠脑中纯化得到的Gi和Goα亚基（Giα和Goα）制剂，然后对肽段进行氨基酸序列分析。用与一个17个氨基酸序列对应的合成探针筛选大鼠C6胶质瘤细胞的cDNA文库，获得了一个编码Goα序列的克隆。接着，用Goα cDNA探针再次筛选该文库，以分离出几个强杂交或弱杂交的克隆。从而获得了编码Giα和Gsα完整序列的cDNA。通过核苷酸序列分析，推导得到了Gsα和Giα的氨基酸序列；它们分别包含394和355个氨基酸残基（包括起始甲硫氨酸）。计算得出Gsα和Giα的分子量分别为45,663和40,499。Goα克隆编码了一个缺少NH2末端的310个氨基酸残基的序列。文中还讨论了Gs、Gi、Go、转导素和ras编码蛋白的α亚基之间的同源性。
