Mycoplasma bovismbfNEncodes a Novel LRR Lipoprotein That Undergoes Proteolytic Processing and Binds Host Extracellular Matrix Components

Abstract

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.

A genome‐wide transposon mutagenesis screening identifies LppB as a key factor associated with Mycoplasma bovis colonization and invasion into host cells

“…Random transposon mutagenesis combined with phenotypic screening is an efficient method for the characterization of functional genes of the M. bovis . Previous studies have reported enolase, TrmFo, Mbov_0503, and mbfN as adhesion‐related proteins of M. bovi s 19–27 . However, few proteins have been confirmed as cytoadhesion‐related proteins at the bacterial level 19,27 .…”

“…Bacterial adhesin is a promising candidate for the development of a vaccine against pathogeny 28–30 . Lipoprotein often plays a pivotal role in the pathogenic bacteria to adhere to host cells 13,19,31 . Pathogenic lipoproteins are considered key factors in activating the humoral immune system of the host and are excellent candidate vaccine targets.…”

“…Previous studies have reported enolase, TrmFo, Mbov_0503, and mbfN as adhesionrelated proteins of M. bovis. [19][20][21][22][23][24][25][26][27] However, few proteins have been confirmed as cytoadhesion-related proteins at the bacterial level. 19,27 Therefore, other adhesion-related factors in M. bovis should be investigated, moreover, the underlying molecular mechanisms responsible for the pathogenicity of M. bovis, that is, adherence to and invasion of host cells, should be elucidated.…”

Mycoplasma Bovis adhesins and their target proteins

“…James and colleagues found that a leucine-rich repetitive lipoprotein (LRR) has adhesin activity ( 43 ). This protein is encoded by the mbfn gene of M. bovis standard strain PG45.…”

“…In addition, this post-translation processing of adhesin is also identified in parasites ( 77 ). In M. bovis adhesins, post-translational processing has also been confirmed ( 43 , 57 ), but the research on this phenomenon is not in-depth. The treatment of adhesin may be closely related to the exposure of adhesin binding sites, immune escape, invasion and toxicity differences.…”