The mompA gene is conserved between Treponema pectinovorum strains

Objectives: To determine if heterogeneity exists between the Major Outer Membrane Protein genes (mompA) of six Treponema pectinovorum strains. Methods: The sequence of mompA from T. pectinovorum ATCC 33768 (GenBank AY007192) was used to construct PCR primers capable of amplifying the structural gene. The primers were used in PCR assays with genomic DNA purified from T. pectinovorum strains ATCC 33768, ATCC 700769, P2, P3, P5, and P8. Restriction fragment length polymorphism (RFLP) analysis determined which mompA sequence differed the greatest from that of ATCC 33768 and that gene was sequenced and compared to the sequence of strain ATCC 33768. Results: PCR reactions using genomic DNA from all six T. pectinovorum strains produced a product with identical electrophoretic mobility of approximately 1,200 base pairs (bp). No product was amplified when genomic DNA isolated from T. denticola, T. vincentii, or T. socranskii was used in the PCR. RFLP analysis determined that the mompA of strain P3 differed from strain ATCC 33768 by the greatest degree and so the mompA gene of strain P3 was sequenced. The mompA structural genes of ATCC 33768 and P3 are 1209 bp and show 95% DNA sequence identity. The translated MompA proteins show 94.3% amino acid (AA) identity and differ at only 23 of 402 positions. Of the 23 amino acids that differ between the predicted proteins only 7 are non-conserved substitutions. Both proteins are predicted to produce a 19 AA signal peptide and produce mature proteins of 40.6 kDa and 40.4 kDa. Conclusions: These strains were isolated from different individuals in the early 1980's (ATCC 33768, P2, P3, P5, P8) and in 1998 (ATCC 7000769). All of these T. pectinovorum strains contain a mompA that is highly conserved. There does not appear to be selective pressure on this species to alter the MompA protein.