Håvarstein L S, Diep D B, Nes I F
Laboratory of Microbial Gene Technology, As, Norway.
Mol Microbiol. 1995 Apr;16(2):229-40. doi: 10.1111/j.1365-2958.1995.tb02295.x.
Lantibiotic and non-lantibiotic bacteriocins are synthesized as precursor peptides containing N-terminal extensions (leader peptides) which are cleaved off during maturation. Most non-lantibiotics and also some lantibiotics have leader peptides of the so-called double-glycine type. These leader peptides share consensus sequences and also a common processing site with two conserved glycine residues in positions -1 and -2. The double-glycine-type leader peptides are unrelated to the N-terminal signal sequences which direct proteins across the cytoplasmic membrane via the sec pathway. Their processing sites are also different from typical signal peptidase cleavage sites, suggesting that a different processing enzyme is involved. Peptide bacteriocins are exported across the cytoplasmic membrane by a dedicated ATP-binding cassette (ABC) transporter. Here we show that the ABC transporter is the maturation protease and that its proteolytic domain resides in the N-terminal part of the protein. This result demonstrates that the ABC transporter has a dual function: (i) removal of the leader peptide from its substrate, and (ii) translocation of its substrate across the cytoplasmic membrane. This represents a novel strategy for secretion of bacterial proteins.
羊毛硫抗生素和非羊毛硫抗生素细菌素作为含有N端延伸序列（前导肽）的前体肽进行合成，这些前导肽在成熟过程中被切除。大多数非羊毛硫抗生素以及一些羊毛硫抗生素具有所谓的双甘氨酸型前导肽。这些前导肽具有共有序列，并且在-1和-2位具有两个保守甘氨酸残基的共同加工位点。双甘氨酸型前导肽与通过sec途径将蛋白质转运穿过细胞质膜的N端信号序列无关。它们的加工位点也不同于典型的信号肽酶切割位点，这表明涉及一种不同的加工酶。肽细菌素通过一种专用的ATP结合盒（ABC）转运蛋白输出穿过细胞质膜。在这里，我们表明ABC转运蛋白是成熟蛋白酶，并且其蛋白水解结构域位于蛋白质的N端部分。这一结果表明ABC转运蛋白具有双重功能：（i）从其底物上切除前导肽，以及（ii）将其底物转运穿过细胞质膜。这代表了一种细菌蛋白分泌的新策略。
