Inouye S, Vlasuk G P, Hsiung H, Inouye M
J Biol Chem. 1984 Mar 25;259(6):3729-33.
Each of the 2 glycine residues in the hydrophobic region of the prolipoprotein signal peptide of Escherichia coli was systematically deleted or substituted with a valine residue by oligonucleotide-directed site-specific mutagenesis. Functional analysis of four such mutants as well as four double mutants, resulting from combinations of any two of the single mutations, revealed that (a) glycine residues at positions 9 and 14 could be replaced individually or at the same time with a valine residue without affecting the secretion of prolipoprotein; (b) the deletion of glycine at position 9 had no effect on the secretion of prolipoprotein whereas, when glycine at position 14 was deleted, the glyceride modification and the processing of the mutant prolipoprotein occurred at a much slower rate at 42 degrees C than those of the wild type prolipoprotein; and (c) the effects of deleting glycine at position 14 could be suppressed by the deletion of glycine at position 9, which resulted in shortening the hydrophobic region of the prolipoprotein signal peptide by 2 amino acid residues. These results indicate that the hydrophobic region of the prolipoprotein signal peptide has remarkable flexibility in terms of the relationship between its primary structure and function in protein secretion.
通过寡核苷酸定向位点特异性诱变，系统地删除了大肠杆菌前脂蛋白信号肽疏水区域中的两个甘氨酸残基，并将其逐个替换为缬氨酸残基。对四个这样的单突变体以及由任意两个单突变组合产生的四个双突变体进行功能分析，结果表明：(a) 第9位和第14位的甘氨酸残基可以单独或同时被缬氨酸残基取代，而不影响前脂蛋白的分泌；(b) 第9位甘氨酸的缺失对前脂蛋白的分泌没有影响，而当第14位甘氨酸缺失时，在42℃下突变前脂蛋白的甘油酯修饰和加工速度比野生型前脂蛋白慢得多；(c) 第14位甘氨酸缺失的影响可以被第9位甘氨酸的缺失所抑制，这导致前脂蛋白信号肽的疏水区域缩短了2个氨基酸残基。这些结果表明，前脂蛋白信号肽的疏水区域在蛋白质分泌中其一级结构与功能的关系方面具有显著的灵活性。
