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Sequence analysis of the major outer membrane protein gene of Chlamydia pneumoniae
M Perez Melgosa1, C C Kuo, L A Campbell
1Department of Pathobiology, University of Washington, Seattle 98195.
Abstract:
Compared with the major outer membrane proteins (MOMPs) of the other chlamydial species, the Chlamydia pneumoniae MOMP appears to be less antigenically complex, and as determined by immunoblot analysis, it does not appear to be the immunodominant antigen recognized during infection. Nucleotide sequence analysis of the C. pneumoniae MOMP gene (ompA) revealed that it consisted of a 1,167-base open reading frame with an inferred 39,344-dalton mature protein of 366 amino acids plus a 23-amino-acid leader sequence. A ribosomal-binding site was located in the 5' upstream region, and two stop codons followed by an 11-base dyad forming a stable stem-loop structure were identified. This sequence shares 68 and 71% DNA sequence homology to the Chlamydia trachomatis serovar L2 and Chlamydia psittaci ovine abortion agent MOMP genes, respectively. Interspecies alignment identified regions, corresponding to the variable domains, which share little sequence similarity with the other chlamydial MOMPs. All seven cysteines conserved in the C. trachomatis and C. psittaci MOMPs, which are involved in the formation of disulfide cross-linkages, are found in the C. pneumoniae MOMP.
Insights
The Chlamydia pneumoniae major outer membrane protein (MOMP) is less antigenically complex than other species and not the primary target during infection. Its gene sequence shows significant homology to related species but unique variable regions.
Area of Science:
- Microbiology
- Immunology
- Genetics
Background:
- The major outer membrane protein (MOMP) is crucial for chlamydial species identification and pathogenesis.
- Previous studies suggested antigenic variation among chlamydial MOMPs, impacting immune responses.
- The specific antigenic profile of Chlamydia pneumoniae MOMP remained less understood.
Purpose of the Study:
- To characterize the Chlamydia pneumoniae MOMP gene (ompA) and its encoded protein.
- To compare the antigenic complexity and immunogenicity of C. pneumoniae MOMP with other chlamydial species.
- To investigate the sequence homology and conserved features of C. pneumoniae MOMP.
Main Methods:
- Nucleotide sequence analysis of the C. pneumoniae ompA gene.
- Inferred protein analysis to determine amino acid sequence and molecular weight.
- Immunoblot analysis to assess antigenic recognition during infection.
- Interspecies sequence alignment of MOMP genes.
Main Results:
- The C. pneumoniae ompA gene encodes a 366-amino acid mature protein with a 23-amino acid leader sequence.
- C. pneumoniae MOMP is less antigenically complex and not immunodominant during infection compared to other chlamydial species.
- The ompA sequence shows 68% and 71% homology to C. trachomatis and C. psittaci MOMP genes, respectively, with conserved cysteine residues but distinct variable regions.
Conclusions:
- The C. pneumoniae MOMP exhibits unique sequence characteristics, including less antigenic complexity.
- Conserved cysteine residues suggest similar disulfide bond formation, important for protein structure.
- Understanding these molecular details aids in differentiating C. pneumoniae and developing targeted diagnostics or therapeutics.