Analysis of a Mycoplasma hominis membrane protein, P120

The monoclonal antibody mAb 26.7D generated against a clinical isolate of Mycoplasma hominis 7488 was shown to react with a surface-exposed epitope on a 120-kDa protein (P120). The gene encoding the protein was cloned and sequenced, and the transcriptional start point was determined by primer extension analysis. The gene contained an open reading frame of 3237 bp encoding a peptide of 1079 amino acids with a deduced molecular mass of 123 kDa. A putative amino-terminal signal peptide and cleavage site for signal peptidase II were found. This suggests that the protein was synthesized as a precursor with subsequent processing to a mature lipoprotein. Surface exposure was confirmed by immunoelectron microscopy. mAb 26.7D reacted with 11 of 19 M. hominis strains. The gene was, however, present in all strains.