Kendall D A, Bock S C, Kaiser E T
Nature. 1986;321(6071):706-8. doi: 10.1038/321706a0.
Proteins secreted by prokaryotic cells are synthesized as precursors containing an amino-terminal extension sequence or signal peptide. Although these signal peptides share little primary sequence homology, recent studies suggest that they function via common pathways during the transport process and that a common element may reside in their secondary structural characteristics. We are investigating the role of an idealized hydrophobic sequence with high potential for alpha-helix formation in the Escherichia coli alkaline phosphatase signal peptide. Here, amino-acid substitutions were made using site-directed mutagenesis to produce a mutant signal sequence containing nine consecutive leucine residues in the hydrophobic core segment. Transport studies with this mutant precursor indicate that mature alkaline phosphatase is correctly targeted to the E. coli periplasm and that processing of the precursor to the mature form of the enzyme is extremely rapid. In contrast, processing is slowed when the mutant signal sequence is lengthened by the insertion of five additional leucine residues and one serine.
原核细胞分泌的蛋白质作为含有氨基末端延伸序列或信号肽的前体进行合成。尽管这些信号肽在一级序列上几乎没有同源性，但最近的研究表明，它们在运输过程中通过共同途径发挥作用，并且一个共同的元件可能存在于它们的二级结构特征中。我们正在研究大肠杆菌碱性磷酸酶信号肽中具有形成α-螺旋高潜力的理想化疏水序列的作用。在这里，使用定点诱变进行氨基酸替换，以产生在疏水核心区段中包含九个连续亮氨酸残基的突变信号序列。对该突变前体的转运研究表明，成熟的碱性磷酸酶被正确地靶向到大肠杆菌周质，并且前体加工成酶的成熟形式非常迅速。相比之下，当通过插入另外五个亮氨酸残基和一个丝氨酸来延长突变信号序列时，加工会减慢。
