Molecular characterization of the Mycoplasma bovis p68 gene, encoding a basic membrane protein with homology to P48 of Mycoplasma agalactiae

Mycoplasmal lipoproteins are considered to be potential virulence determinants, which may carry out numerous important functions in pathogenesis including adhesion and immunomodulation. The prototype mycoplasmal immunomodulin is the macrophage-activating lipoprotein (MALP) of Mycoplasma fermentans. In this study, a homolog of the malp gene, designated p68, was identified and characterized in Mycoplasma bovis strain PG45 clonal variant #6. P68 belongs to the family of basic membrane proteins, which have been identified in diverse prokaryotes, including mycoplasmas. P68 revealed significant similarity and shared conserved selective lipoprotein-associated motifs with the highly immunogenic MALP-related lipoproteins P48 of M. bovis and P48 of Mycoplasma agalactiae. Determination of the genomic distribution of both M. bovis malp-homologs showed that p48 was present in all M. bovis strains tested, whereas the p68 gene was missing in some. Sequence comparison of the p68 genomic region in strains with and without this gene revealed that the region is very dynamic, with multiple genetic changes. Reverse-transcription PCR and primer extension analysis indicated that both p68 and p48 are transcribed in M. bovis under in vitro growth conditions. Mycoplasma bovis is the first mycoplasma species in which two malp-related genes have been identified.