Mm19, a Mycoplasma meleagridis Major Surface Nuclease that Is Related to the RE_AlwI Superfamily of Endonucleases

Abstract

Mycoplasma meleagridis infection is widespread in turkeys, causing poor growth and feathering, airsacculitis, osteodystrophy, and reduction in hatchability. Like most mycoplasma species, M. meleagridis is characterized by its inability to synthesize purine and pyrimidine nucleotides de novo. Consistent with this intrinsic deficiency, we here report the cloning, expression, and characterization of a M. meleagridis gene sequence encoding a major surface nuclease, referred to as Mm19. Mm19 consists of a 1941- bp ORF encoding a 646-amino-acid polypeptide with a predicted molecular mass of 74,825 kDa. BLASTP analysis revealed a significant match with the catalytic/dimerization domain of type II restriction enzymes of the RE_AlwI superfamily. This finding is consistent with the genomic location of Mm19 sequence, which dispalys characteristics of a typical type II restriction-modification locus. Like intact M. meleagridis cells, the E. coli-expressed Mm19 fusion product was found to exhibit a nuclease activity against plasmid DNA, double-stranded DNA, single-stranded DNA, and RNA. The Mm19-associated nuclease activity was consistently enhanced with Mg2+ divalent cations, a hallmark of type II restriction enzymes. A rabbit hyperimmune antiserum raised against the bacterially expressed Mm19 strongly reacted with M. meleagridis intact cells and fully neutralized the surface-bound nuclease activity. Collectively, the results show that M. meleagridis expresses a strong surface-bound nuclease activity, which is the product of a single gene sequence that is related to the RE_AlwI superfamily of endonucleases.

Extracellular DNA: A Nutritional Trigger of Mycoplasma bovis Cytotoxicity

“…The importance of eDNA in the biology of M. bovis is consistent with functional genomic studies with several ruminant mycoplasma species that identified nucleotide metabolism as essential for their survival in cell culture, while dispensable for axenic growth (Baranowski et al, 2010; Skapski et al, 2011; Josi et al, 2019). Finally, nucleases and polynucleotide binding proteins are common component of the mycoplasma surface, besides their role in the acquisition of nutrients these surface proteins are also emerging as potential virulence factors (Minion and Goguen, 1986; Minion et al, 1993; Bendjennat et al, 1999; Jarvill-Taylor et al, 1999; Schmidt et al, 2007; Li et al, 2010, 2018, 2019a; Somarajan et al, 2010; Szczepanek et al, 2010; Browning et al, 2011; Cacciotto et al, 2013, 2019; Masukagami et al, 2013; Sharma et al, 2015; Xu et al, 2015; Yacoub and Mardassi, 2016; Zhang et al, 2016; Gondaira et al, 2017; Yamamoto et al, 2017; Mitiku et al, 2018; Qin et al, 2019).…”

Infection strategies of mycoplasmas: Unraveling the panoply of virulence factors

“…The first nuclease was identified approximately 20 years ago. Since then, a number of similar enzymes or homologous genes have also been reported in M. pneumoniae [17,102,[120][121][122][123][124][125][126][127][128][129]. Some of the characterized nucleases are listed in Table 2.…”

Neutrophil extracellular traps in bacterial infections and evasion strategies

“…Nucleases are a crucial component of Mycoplasma pathogenesis, facilitating bacterial growth and persistence in the host by digesting host nucleic acids and producing free nucleotide precursors (140-142). Membrane-associated or secreted nucleases have been found in many Mycoplasma species (129,132,(143)(144)(145)(146), and are homologous to staphylococcal nuclease (101). Mycoplasma lipoproteins are a major determinants of NET release during the innate immune response (39).…”