Identification by sequence analysis of two-site posttranslational processing of the cysteine-rich outer membrane protein 2 of Chlamydia trachomatis serovar L2

Abstract

The 60,000-molecular-weight cysteine-rich outer membrane protein (OMP2) from Chiamydia trachomatis participates in the disulfide-mediated outer-membrane organization unique to this organism. In addition, this protein is a primary focus of the host immune response. We cloned and sequenced the gene Infections by Chlamydia trachomatis are a leading cause of sexually transmitted disease, infertility, and blindness. Within the species, two biovars have been described which are responsible for human disease (19). The trachoma biovar infects mucosal epithelial cells and produces localized infection of the urogenital tract and eyes. The lymphogranuloma venereum (LGV) biovar has broader host cell specificity and causes more invasive sexually transmitted disease. Chlamydiae have a unique life cycle in which the bacteria alternate between two developmental forms, the extracellular elementary body (EB) and the intracellular reticulate body. Only the EB is capable of extracellular survival, host cell recognition, and invasion, suggesting a fundamental role for EB outer membrane constituents in infectivity.The differences in infectivity observed between the trachoma and LGV biovars may be mediated by dissimilarity in outer membrane composition, variation in primary structure of the EB constituents, or higher-ordered structural heterogeneity. The EB outer membrane contains three cysteinerich proteins with molecular weights of about 40,000 (MOMP), 60,000 (OMP2), and 15,000. The chlamydial cell envelope lacks a peptidoglycan layer for structural integrity (2). It has been proposed that in its absence inter-and intramolecular disulfide bonding among the cysteine-rich proteins imparts rigidity to the EB outer membrane (22).Complete sequence information for the MOMP-encoding genes of several serotypes (25,26) indicates that this protein is antigenically complex, possessing species-, subspeciesand serovar-specific epitopes on each molecule (28). The 15,000-molecular-weight cysteine-rich protein has recently been described as possessing both biovar-and speciesspecific epitopes (31). To date, the epitopes identified on the 60,000-molecular-weight outer-membrane protein by monoclonal antibodies have all been species specific, demonstrating less antigenic diversity than the other cysteine-rich proteins (20). * Corresponding author.Despite the evidence for a shared antigenic structure, there are several striking physical differences between the 60,000-molecular-weight proteins of the trachoma biovar and the more invasive LGV biovar. This protein appears as a predominant single band in gel electrophoresis of trachoma strains but is present as a less intense doublet in LGV strains (3). Recently, peptide maps have demonstrated that there are significant structural differences between the proteins of these two biovars (20). Further, it has been observed that the 60,000-molecular-weight protein of the trachoma biovar has a nearly neutral isoelectric point (pl), whereas the LGV proteins have a net positive charge, with a pl of 8.5 to 9.0 (3)...

Genomic transcriptional profiling of the developmental cycle of Chlamydia trachomatis

“…These genes encode proteins with homology to adenoviral proteases (as described on the Los Alamos STD Sequence Database at www.stdgen.lanl.gov), which have proteolytic roles in maturation of virus particles (42). A key protein component of the OM complex, the OmcB protein, has been shown to undergo posttranslational proteolytic processing (43)(44)(45). Although it is unknown whether the observed processing occurs through the membrane thiol proteases described here, we hypothesize that their coexpression, late in the developmental cycle, may be important in OM complex formation.…”

Chlamydia trachomatis Serology: Diagnostic Value of Outer Membrane Protein 2 Compared with That of Other Antigens

“…A 1,644-bp fragment (GenBank accession no. M23001) was amplified (1). Oligonucleotides used as primers were designed with 5Ј NcoI (5Ј-CATGccatggAC AAACTCATCAGACGAGCAGTGACG-3Ј) and 3Ј BamHI (5Ј-CGggatccATA GATGTGTGTATTCTCTGTATCA-3Ј) restriction endonuclease sites (lowercase letters) and were synthesized by Microsynth (Balgach, Switzerland).…”

Human CD8+ T Cells Recognize the 60-kDa Cysteine-Rich Outer Membrane Protein fromChlamydia trachomatis

“…OmcB (CT443) is a 553-aa residue protein also referred to as the 60-kDa cysteine-rich outer membrane protein. This protein is highly conserved among the C. trachomatis serovars (19,(32)(33)(34)(35), sharing between 98 and 99% aa sequence identity. OmcB from C. trachomatis shares ϳ71% aa sequence identity with its homologue in C. pneumoniae (36).…”