Russel M, Kaźmierczak B
Rockefeller University, New York, New York 10021.
J Bacteriol. 1993 Jul;175(13):3998-4007. doi: 10.1128/jb.175.13.3998-4007.1993.
The gene IV protein of filamentous bacteriophages is an integral membrane protein required for phage assembly and export. A series of gene IV::phoA fusion, gene IV deletion, and gene IV missense mutations have been isolated and characterized. The alkaline phosphatase activity of the fusion proteins suggests that pIV lacks a cytoplasmic domain. Cell fractionation studies indicate that the carboxy-terminal half of pIV mediates its assembly into the membrane, although there is no single, discrete membrane localization domain. The properties of gene IV missense and deletion mutants, combined with an analysis of the similarities between pIVs from various filamentous phage and related bacterial export-mediating proteins, suggest that the amino-terminal half of pIV consists of a periplasmic substrate-binding domain that confers specificity to the assembly-export system.
丝状噬菌体的基因IV蛋白是噬菌体组装和输出所必需的整合膜蛋白。已分离并鉴定了一系列基因IV::phoA融合、基因IV缺失和基因IV错义突变。融合蛋白的碱性磷酸酶活性表明pIV缺乏细胞质结构域。细胞分级分离研究表明，pIV的羧基末端一半介导其组装到膜中，尽管没有单一的、离散的膜定位结构域。基因IV错义突变体和缺失突变体的特性，结合对来自各种丝状噬菌体的pIV与相关细菌输出介导蛋白之间相似性的分析，表明pIV的氨基末端一半由周质底物结合结构域组成，该结构域赋予组装-输出系统特异性。
