Dierstein R, Gad'on N
Institut für Biologie 2-Mikrobiologie, Albert-Ludwigs-Universität, Freiburg, Federal Republic of Germany.
Arch Microbiol. 1993;159(2):101-8. doi: 10.1007/BF00250267.
Synthesis and assembly of leader peptidase of Escherichia coli (signal peptidase I), was studied by heterologous expression of its lep gene in three species of phototrophic purple bacteria. Cell extracts of the recipient species showed neither cross reaction with antibodies against E. coli leader peptidase nor cleavage of the model substrate M13-procoat in vitro. The lep gene was transferred via conjugation using the plasmid expression vector for phototrophic bacteria pJAJ9. Plasmid-borne leader peptidase enzyme was identified by immunochemical means. However, extracts of transconjugant cells showed no cleavage function. Trypsin digestion studies revealed that the enzyme was not properly integrated across the host membranes. The data suggest that cleaving enzymes for protein export and/or their assembly pathway in purple bacteria differ from the E. coli type.
通过在三种光合紫色细菌中异源表达其lep基因，对大肠杆菌的前导肽酶（信号肽酶I）的合成和组装进行了研究。受体菌的细胞提取物在体外既不与抗大肠杆菌前导肽酶的抗体发生交叉反应，也不切割模型底物M13-前衣壳。使用光合细菌的质粒表达载体pJAJ9通过接合转移lep基因。通过免疫化学方法鉴定了质粒携带的前导肽酶。然而，转接合子细胞的提取物没有切割功能。胰蛋白酶消化研究表明，该酶没有正确整合到宿主膜中。数据表明，紫色细菌中用于蛋白质输出的切割酶和/或其组装途径与大肠杆菌类型不同。
