Giam C Z, Chai T, Hayashi S, Wu H C
Eur J Biochem. 1984 Jun 1;141(2):331-7. doi: 10.1111/j.1432-1033.1984.tb08196.x.
An Escherichia coli mutant (lpp-14-1), with an alteration of glycine to aspartic acid at the 14th amino acid residue of the prolipoprotein signal sequence, has previously been shown to contain unmodified and unprocessed prolipoprotein in its cell envelope. Both the wild-type and the lpp-14-1 alleles of the lpp gene have been cloned onto a phage lambda vector. Two pseudorevertant alleles of lpp-14-1 (14R21 and 6a) have been isolated, cloned and sequenced. Amino acid sequences, deduced from the DNA sequences of the two revertant lipoprotein alleles, and biochemical characterization of the revertant lipoproteins, show that a conversion of the aspartic acid (residue 14) to asparagine completely restores the modification and processing of the 14R21 revertant prolipoprotein, while a change of the threonine-16 to isoleucine-16 partially enhances the modification and processing of the 6a prolipoprotein, which retains the aspartate-14 substitution. Secondary structure analysis of the revertant prolipoprotein signal sequences according to the Chou and Fasman rules revealed that the specific coil region in residues 14 and 15, and the beta-sheet structure in residues 16-18 of signal sequence may be important for prolipoprotein modification. These results suggest essential roles of both a unique secondary structure and hydrophobicity in residues 14-18 of prolipoprotein signal sequence for the proper recognition by the glyceryl transferase.
大肠杆菌突变体（lpp - 14 - 1）在原脂蛋白信号序列的第14个氨基酸残基处发生了甘氨酸到天冬氨酸的改变，先前已表明其细胞膜中含有未修饰和未加工的原脂蛋白。lpp基因的野生型和lpp - 14 - 1等位基因都已克隆到噬菌体λ载体上。已分离、克隆并测序了lpp - 14 - 1的两个假回复等位基因（14R21和6a）。从两个回复脂蛋白等位基因的DNA序列推导的氨基酸序列以及回复脂蛋白的生化特性表明，天冬氨酸（残基14）到天冬酰胺的转变完全恢复了14R21回复原脂蛋白的修饰和加工，而苏氨酸 - 16到异亮氨酸 - 16的变化部分增强了保留天冬氨酸 - 14替代的6a原脂蛋白的修饰和加工。根据Chou和Fasman规则对回复原脂蛋白信号序列进行的二级结构分析表明，信号序列中残基14和15的特定卷曲区域以及残基16 - 18的β - 折叠结构可能对原脂蛋白修饰很重要。这些结果表明，原脂蛋白信号序列残基14 - 18中的独特二级结构和疏水性对于甘油转移酶的正确识别都起着重要作用。
