Geli V, Baty D, Crozel V, Morlon J, Lloubes R, Pattus F, Lazdunski C
Mol Gen Genet. 1986 Mar;202(3):455-60. doi: 10.1007/BF00333276.
A plasmid (pColAF1), derived from pColA, and lacking the region encoding Cai (colicin A immunity protein) and Cal (colicin A lysis protein) has been constructed. The strains carrying pColAF1 produce normal amounts of colicin A which remains in the cell cytoplasm and does not result in loss of viability. Similar results have also been obtained for transposon insertion mutants lacking Cai. Structure prediction analysis indicates that four peptide regions of Cai might span the cytoplasmic membrane. Since the NH2- and COOH-terminal regions are charged, this analysis suggests a topology of the 178 residues polypeptide chain in which regions 38 to 70 and 124 to 143 might be exposed at the outer side of the cytoplasmic membrane. With mutants constructed using recombinant DNA techniques, we could demonstrate that the removal of a 30 residue COOH-terminal region, and mutations altering the surface exposed loop comprised of aminoacid residues 124-143 abolish the protecting function of Cai.
构建了一种源自pColA的质粒（pColAF1），该质粒缺失编码蔡（大肠杆菌素A免疫蛋白）和卡尔（大肠杆菌素A裂解蛋白）的区域。携带pColAF1的菌株产生正常量的大肠杆菌素A，其保留在细胞质中，不会导致活力丧失。对于缺乏蔡的转座子插入突变体也获得了类似结果。结构预测分析表明，蔡的四个肽区域可能跨越细胞质膜。由于NH2和COOH末端区域带电荷，该分析表明178个残基多肽链的拓扑结构，其中区域38至70和124至143可能暴露在细胞质膜外侧。通过使用重组DNA技术构建的突变体，我们可以证明去除30个残基的COOH末端区域以及改变由氨基酸残基124 - 143组成的表面暴露环的突变会消除蔡的保护功能。
