Dascher C, Roll D, Bavoil P M
Department of Microbiology and Immunology, University of Rochester Medical Center, NY 14642.
Microb Pathog. 1993 Dec;15(6):455-67. doi: 10.1006/mpat.1993.1094.
The entire gene encoding the major outer membrane protein (MOMP) from Chlamydia psittaci strain GPIC has been cloned and expressed in Escherichia coli. A tightly regulated T7 promoter is used to control expression of the protein in Escherichia coli. Upon induction of expression, the precursor (pre-MOMP) is synthesized in the cell. This is followed by the appearance of a lower molecular weight protein that comigrates with mature MOMP from chlamydial elementary bodies by both one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. When E. coli cells expressing MOMP are converted to spheroplasts and subjected to protease treatment, MOMP is quantitatively degraded while cytoplasmic pre-MOMP is protected from degradation. Whole cells subjected to the same protease treatment show no degradation of MOMP. Furthermore, MOMP is not detected in surface-labeling experiments using several MOMP-specific antibodies. These data indicate that pre-MOMP is translocated to the periplasmic space and processed but is not surface exposed in E. coli. Expression of MOMP in this system causes a significant reduction in cell viability. In addition, coexpression in E. coli of MOMP or a MOMP-PhoA fusion with various chaperone proteins does not alter the level of MOMP translocation.
鹦鹉热衣原体菌株GPIC的主要外膜蛋白（MOMP）的完整编码基因已被克隆并在大肠杆菌中表达。一个严格调控的T7启动子用于控制该蛋白在大肠杆菌中的表达。诱导表达后，前体（前-MOMP）在细胞中合成。随后出现一种分子量较低的蛋白，通过一维十二烷基硫酸钠聚丙烯酰胺凝胶电泳和二维凝胶电泳，它与衣原体原体中的成熟MOMP迁移率相同。当表达MOMP的大肠杆菌细胞转化为原生质球并进行蛋白酶处理时，MOMP被定量降解，而细胞质中的前-MOMP受到保护不被降解。经过相同蛋白酶处理的全细胞未显示MOMP降解。此外，在使用几种MOMP特异性抗体的表面标记实验中未检测到MOMP。这些数据表明，前-MOMP被转运到周质空间并进行了加工，但在大肠杆菌中未暴露于表面。该系统中MOMP的表达导致细胞活力显著降低。此外，MOMP或MOMP-PhoA融合蛋白与各种伴侣蛋白在大肠杆菌中的共表达不会改变MOMP的转运水平。
