Por Secretion System-Dependent Secretion and Glycosylation of Porphyromonas gingivalis Hemin-Binding Protein 35

Abstract

The anaerobic Gram-negative bacterium Porphyromonas gingivalis is a major pathogen in severe forms of periodontal disease and refractory periapical perodontitis. We have recently found that P. gingivalis has a novel secretion system named the Por secretion system (PorSS), which is responsible for secretion of major extracellular proteinases, Arg-gingipains (Rgps) and Lys-gingipain. These proteinases contain conserved C-terminal domains (CTDs) in their C-termini. Hemin-binding protein 35 (HBP35), which is one of the outer membrane proteins of P. gingivalis and contributes to its haem utilization, also contains a CTD, suggesting that HBP35 is translocated to the cell surface via the PorSS. In this study, immunoblot analysis of P. gingivalis mutants deficient in the PorSS or in the biosynthesis of anionic polysaccharide-lipopolysaccharide (A-LPS) revealed that HBP35 is translocated to the cell surface via the PorSS and is glycosylated with A-LPS. From deletion analysis with a GFP-CTD[HBP35] green fluorescent protein fusion, the C-terminal 22 amino acid residues of CTD[HBP35] were found to be required for cell surface translocation and glycosylation. The GFP-CTD fusion study also revealed that the CTDs of CPG70, peptidylarginine deiminase, P27 and RgpB play roles in PorSS-dependent translocation and glycosylation. However, CTD-region peptides were not found in samples of glycosylated HBP35 protein by peptide map fingerprinting analysis, and antibodies against CTD-regions peptides did not react with glycosylated HBP35 protein. These results suggest both that the CTD region functions as a recognition signal for the PorSS and that glycosylation of CTD proteins occurs after removal of the CTD region. Rabbits were used for making antisera against bacterial proteins in this study.

Helical flow of surface protein required for bacterial gliding motility

“…Comparative genome analysis reveals the widespread occurrence of PorSS genes in members of the phylum Bacteroidetes and their absence in members of other bacterial phyla (5). The secretion mechanism and protein components of PorSSs are distinct from those of the type I-VIII secretion systems (4,5,32), resulting in the use of T9SS to describe this Bacteroidetes-specific secretion system.…”

New Family of Ulvan Lyases Identified in Three Isolates from the Alteromonadales Order

“…The short version is composed of a catalytic module with signal peptide, whereas the long ulvan lyase also comprises a Por secretion system (recently renamed type IX secretion system) C-terminal sorting domain sequence. The C-terminal sorting domain mediates protein secretion by the type IX secretion system, a system that is unique to the Bacteroidetes phylum (22)(23)(24)(25). Flavobacterium johnsoniae, which also belongs to the Bacteroidetes phylum, utilizes the type IX secretion system both for gliding motility and for extracellular chitinase secretion (26).…”

Biochemical and Structural Characterization of the Complex Agarolytic Enzyme System from the Marine Bacterium Zobellia galactanivorans

“…1B). AgaA and AgaD are modular proteins, containing N-terminal signal peptides targeting the periplasmic space and a C-terminal domain only conserved in Bacteroidetes (43) and likely acting as a sorting signal for a secretion system unique to this phylum (44,45). AgaB and AgaC both contain a lipoprotein-type signal peptide that targets the outer membrane.…”

“…7). In this picture AgaD, which displays a C-terminal Bacteroidetes-specific domain (43,45), could be secreted in the external medium or displayed at the surface of Z. galactanivorans only in the presence of low sulfated agars (Fig. 6).…”