Mycoplasma bovis mbfN encodes a novel LRR lipoprotein that undergoes proteolytic processing and binds host extracellular matrix components.

Mycoplasma bovis cause serious infection in ruminants leading to huge economic losses. Lipoproteins are key components of mycoplasma membrane and are believed to function in nutrient acquisition, adherence, enzymatic interaction with the host and inducing the host immune response to infection. Genomic data arising from M. bovis show that many of the genes are not assigned any functions, owing in part to their low sequence similarity to those of other bacteria making it difficult to extrapolate gene functions. This study identifies a surface localised LRR lipoprotein encoded by mbfN of M. bovis PG45. Homologues of MbfN were detected as a 48-kDa peptide on Western blot of all strains of M. bovis and the predicted 70 kDa full-length polypeptide in some strains included in this study. Sequence analysis of the gene revealed the absence of a region encoding the carboxyl terminal 147 amino acids in some strains when compared with PG45, which could account for the variation detected on immunoblot. In silico analysis of MbfN suggest that it may have an adhesion-related function. In vitro binding assays confirmed MbfN to be a fibronectin and heparin binding protein. Disruption of mbfN in M. bovis PG45 significantly reduced (P = 0.033) the adherence of M. bovis PG45 to MDBK cells in vitro, showing the contribution of MbfN as an adhesin.IMPORTANCE: Experimental validation of putative functions of a particular gene in M. bovis will advance our understanding of the basic biology of this economically important pathogen, which is crucial in developing prevention strategies. This study demonstrates the extracellular matrix binding ability of a novel immunogenic lipoprotein of M. bovis and the contribution of this protein in adhesion of M. bovis suggest that it could play a role in virulence.