Structural and functional probing of PorZ, an essential bacterial surface component of the type-IX secretion system of human oral-microbiomic Porphyromonas gingivalis.

• DOI: 10.1038/srep37708
• Publication Date: 2016-11-24T10:15:19Z
• Authors: Anna M. Lasica; Theodoros Goulas; Danuta Mizgalska; Xiaoyan Zhou; Iñaki de Diego; Mirosław Ksiazek; Mariusz Madej; Yonghua Guo; Tibisay Guevara; Magdalena Nowak; Barbara Potempa; Apoorv Goel; Maryta Sztukowska; Apurva T. Prabhakar; Monika Bzowska; Magdalena Widziolek; Ida B. Thøgersen; Jan J. Enghild; Mary Simonian; Arkadiusz W. Kulczyk; Ky-Anh Nguyen; Jan Potempa; F. Xavier Gomis-Rüth
• Keywords: 570; 610; Crystallography, X-Ray; Article; Protein Structure, Secondary; 03 medical and health sciences; Bacterial Proteins; Protein Domains; Escherichia coli; Humans; Amino Acid Sequence; Adhesins, Bacterial; Bacterial Secretion Systems; X-ray crystallography; Mouth; 0303 health sciences; Pigmentation; Microbiota; Cell Membrane; Bacteriology; Cysteine Endopeptidases; Phenotype; Gingipain Cysteine Endopeptidases; Protein-Arginine Deiminases; Pathogens; Porphyromonas gingivalis; Protein Processing, Post-Translational; Gene Deletion

AbstractPorphyromonas gingivalis is a member of the human oral microbiome abundant in dysbiosis and implicated in the pathogenesis of periodontal (gum) disease. It employs a newly described type-IX secretion system (T9SS) for secretion of virulence factors. Cargo proteins destined for secretion through T9SS carry a recognition signal in the conserved C-terminal domain (CTD), which is removed by sortase PorU during translocation. Here, we identified a novel component of T9SS, PorZ, which is essential for surface exposure of PorU and posttranslational modification of T9SS cargo proteins. These include maturation of enzyme precursors, CTD removal and attachment of anionic lipopolysaccharide for anchorage in the outer membrane. The crystal structure of PorZ revealed two β-propeller domains and a C-terminal β-sandwich domain, which conforms to the canonical CTD architecture. We further documented that PorZ is itself transported to the cell surface via T9SS as a full-length protein with its CTD intact, independently of the presence or activity of PorU. Taken together, our results shed light on the architecture and possible function of a novel component of the T9SS. Knowledge of how T9SS operates will contribute to our understanding of protein secretion as part of host-microbiome interactions by dysbiotic members of the human oral cavity.