Using Escherichia coli as a Method for Studying the Major Outer Membrane Protein of Chlamydia trachomatis
Chlamydia trachomatis is the major cause of preventable blindness and a common agent of sexually transmitted disease. The most abundant outer membrane component of Chlamydia trachomatis is the major outer membrane protein (MOMP). MOMP is believed to play an important role in maintaining the structure of the chlamydial outer membrane and is a candidate for subunit vaccine development. The gene encoding MOMP was expressed in Escherichia coli and evaluated as a method for studying MOMP structure and function. The growth properties and expression of E. coli containing variations of the C. trachomatis MOMP gene were analyzed with growth curves, Western blots and cell fractionation experiments. E. coli cells with the plasmids pTTQ-W, pTTQ-H, and pTTQ-F were lysed after induction with IPTG and analyzed for MOMP expression. Cells carrying the plasmid pTTQ-W had less MOMP expression then cells carrying plasmids pTTQ-H and pTTQ-F. Fusion of the MOMP gene to the amino terminal end of the E. coli OmpA gene in the pTTQ-H and pTTQ-F plasmids resulted in an increased level of MOMP expression but did not prevent cells from lysing. The cell fractionation experiments showed that the MOMP proteins expressed by each plasmid (pTTQ-W, pTTQ-H, and pTTQ-F) were present in the outer membrane fraction. These results would suggest that the recombinant MOMP proteins produced by these plasmids are making it to the outer membrane and are somehow disrupting cell growth so that the cells are being lysed.