Agterberg M, van Die I, Yang H, Andriessen J A, van Tetering A, van den Eijnden D H, Ploegh H L
Department of Medical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
Eur J Biochem. 1993 Oct 1;217(1):241-6. doi: 10.1111/j.1432-1033.1993.tb18239.x.
Three cDNA clones encoding small GTP-binding proteins, LS-Rab1, LS-Rab2 and LS-Rab18a were isolated from a cDNA library from the albumen gland of the pulmonate snail Lymnaea stagnalis. Comparison of the deduced amino acid sequences with available sequences from the EMBL/Data Bank revealed that LS-Rab1 and LS-Rab2 show a sequence identity of 89-90% to the mammalian Rab1 and Rab2 proteins, and can therefore be regarded as the L. stagnalis homologs. LS-Rab18a may be considered a new member of the Rab subfamily, closely related to mouse Rab18 (74% amino acid identity). Interestingly, LS-Rab1 and LS-Rab2 share a very high sequence conservation with their mammalian homologs (95-97%) over the first 178-191 N-terminal amino acids, whereas the C-terminal part is almost completely divergent, except for their extreme ends (2-4 amino acids). The implications of these observations for the understanding of Rab-targeting signals are discussed. The LS-rab cDNAs were expressed in COS-7M6 cells. The resulting 22-kDa products were shown to bind GTP. In the albumen gland mRNA, levels of LS-rab1 appeared to be much higher than those of LS-rab2 and LS-rab18a, suggesting an important role for the LS-Rab1 protein in the albumen gland.
从肺螺亚纲椎实螺（Lymnaea stagnalis）蛋白腺的cDNA文库中分离出了三个编码小GTP结合蛋白的cDNA克隆，即LS-Rab1、LS-Rab2和LS-Rab18a。将推导的氨基酸序列与EMBL/数据库中的现有序列进行比较后发现，LS-Rab1和LS-Rab2与哺乳动物的Rab1和Rab2蛋白的序列同一性为89%-90%，因此可被视为椎实螺的同源物。LS-Rab18a可能被认为是Rab亚家族的一个新成员，与小鼠Rab18密切相关（氨基酸同一性为74%）。有趣的是，LS-Rab1和LS-Rab2在其N端的前178-191个氨基酸上与其哺乳动物同源物具有非常高的序列保守性（95%-97%），而C端部分几乎完全不同，除了其末端（2-4个氨基酸）。讨论了这些观察结果对理解Rab靶向信号的意义。LS-rab cDNA在COS-7M6细胞中表达。结果显示产生的22 kDa产物能结合GTP。在蛋白腺mRNA中，LS-rab1的水平似乎远高于LS-rab2和LS-rab18a，这表明LS-Rab1蛋白在蛋白腺中具有重要作用。
