Morishita R, Masuda K, Niwa M, Kato K, Asano T
Department of Biochemistry, Institute for Development Research, Aichi Prefectural Colony, Japan.
Biochem Biophys Res Commun. 1993 Aug 16;194(3):1221-7. doi: 10.1006/bbrc.1993.1953.
We reported previously that G proteins from bovine spleen contain at least five forms of the gamma subunit (designated S1 through S5), among which S1 and S5 have been identified as novel gamma and gamma 2 subunits, respectively. In this study, we identified the other three forms of the gamma subunit, namely, S2, S3 and S4. Amino acid sequences of proteolytic fragments obtained from S2, S3 and S4 coincided exactly with internal sequences of gamma 7, gamma 5 and gamma 2, respectively. However, sequence analysis of undigested S4 revealed that S4 was an N-terminally truncated form of gamma 2, while analysis of the C-terminal fragment by fast atom bombardment mass spectrometry revealed that the C-terminus of S4 seemed to be geranylgeranylated and carboxymethylated as is that of intact gamma 2. Thus, the three types of gamma subunit obtained from bovine spleen were identified as gamma 7, gamma 5, and an N-terminally truncated gamma 2.
我们之前报道过，牛脾脏的G蛋白包含至少五种γ亚基形式（命名为S1至S5），其中S1和S5已分别被鉴定为新型γ亚基和γ2亚基。在本研究中，我们鉴定出了γ亚基的其他三种形式，即S2、S3和S4。从S2、S3和S4获得的蛋白水解片段的氨基酸序列分别与γ7、γ5和γ2的内部序列完全一致。然而，未消化的S4的序列分析表明，S4是γ2的N端截短形式，而通过快原子轰击质谱对C端片段的分析表明，S4的C端似乎像完整的γ2一样被香叶基香叶基化和羧甲基化。因此，从牛脾脏获得的三种γ亚基类型被鉴定为γ7、γ5和N端截短的γ2。
