The outer-membrane protein MafA of Neisseria meningitidis constitutes a novel protein secretion pathway specific for the fratricide protein MafB

Virulence

Laura Catón¹  Tom van den Hoeven¹  Vincent de Maat¹  Juan Cruz Herrero¹  Jan Tommassen¹  Jesús Arenas² 

[1] Section Molecular Microbiology, Department of Biology, Utrecht University, Utrecht, Netherland;Section Molecular Microbiology, Department of Biology, Utrecht University, Utrecht, Netherland;Unit of Microbiology and Immunology, Faculty of Veterinary, University of Zaragoza, Zaragoza, Spai;

关键词: Interbacterial competition;    MafA;    MafB;    Neisseria;    protein secretion;    secretome;    toxin;   

DOI  :  10.1080/21505594.2020.1851940

来源: Taylor & Francis

【 摘 要 】

MafB proteins are toxins secreted by Neisseria spp. which are involved in interbacterial competition. Their secretion mechanism has so far not been elucidated. Each strain can produce several MafB variants. On the chromosome, the mafB genes are localized on genomic islands also containing mafA genes. MafA proteins have a role in virulence with reported activities in adhesion and transcytosis of pathogenic Neisseria, a priori unrelated to MafB activities. In this study, we investigated the possible involvement of MafA in the transport of MafB across the outer membrane of Neisseria meningitidis. In wild-type strains, proteolytic fragments of MafB proteins were detected in the extracellular medium. In the absence of MafA, secretion was abrogated, and, in the case of MafBI, full-length and truncated polypeptides were detected inside the cells and inside outer-membrane vesicles. MafBI secretion required its cognate MafA, whereas MafBIII could use any MafA. Heterologous expression in Escherichia coli showed that MafBIII is transported to a cell-surface-exposed, i.e. protease-accessible, location in a MafA-dependent way. MafA itself was found to be localized to the outer membrane, forming large oligomeric complexes. As homologs were found in diverse bacteria, the Maf system represents a new protein secretion system in Gram-negative bacteria.

【 授权许可】

CC BY