Differential domains and endoproteolytic processing in dominant surface proteins of unknown function from Mycoplasma hyopneumoniae and Mycoplasma flocculare

Mycoplasma hyopneumoniae causes porcine enzootic pneumonia (PEP), a chronic respiratory disease that leads to severe economic losses in the pig industry. Swine infection and PEP devel-opment depend on the adhesion of the pathogen to the swine respiratory tract and the host im -mune response, but these and other disease determinants are not fully understood. For instance, M. hyopneumoniae has a large repertoire of proteins of unknown function (PUFs) and some of them are abundant in the cell surface, where they likely mediate so far unknown pathogen-host interactions. Moreover, these surface PUFs may undergo endoproteolytic processing to generate larger repertoires of proteoforms to further complicate this scenario. Here, we investigated the five PUFs more represented on the surface of M. hyopneumoniae pathogenic strain 7448 in comparison with their orthologs from the nonpathogenic M. hyopneumoniae J strain and the closely related commensal species Mycoplasma flocculare. Comparative in silico analyses of deduced amino acid sequences and proteomic data identified differential domains, disordered regions and repeated motifs. We also provide evidence of differential endoproteolytic processing and antigenicity. Phylogenetic analyses were also performed with ortholog sequences, showing higher conservation of three of the assessed PUFs among Mycoplasma species related to respira-tory diseases. Overall, our data point out to M. hyopneumoniae surface-dominant PUFs likely associated with pathogenicity.

Automated summary

Mycoplasma hyopneumoniae possesses surface proteins of unknown function (PUFs) that may play a role in the pathogenicity of porcine enzootic pneumonia (PEP). This study compared the expression of five PUFs in the pathogenic strain 7448 of M. hyopneumoniae with their orthologs from nonpathogenic M. hyopneumoniae J strain and a closely related commensal species Mycoplasma flocculare. Analysis of amino acid sequences and proteomic data revealed differential domains, disordered regions, and repeated motifs. Differential endoproteolytic processing and antigenicity were also observed. Phylogenetic analysis showed higher conservation of three PUFs among Mycoplasma species related to respiratory diseases.