P. gingivalis
not annotated - annotated - LINNAEUS only
20971915
C-terminal domain residues important for secretion and attachment of RgpB in Porphyromonas gingivalis.
Porphyromonas gingivalis, a periodontal pathogen, expresses a group of surface proteins with a common C-terminal domain (CTD) that are exported by a novel secretion system to the surface, where they are covalently attached. Using RgpB as a model CTD protein, we have produced a series of site-directed mutations in the CTD sequence at conserved residues and at residues that may be modified and, hence, surface attached. The mutant RgpB proteins were expressed in a P. gingivalis host lacking functional RgpB and RgpA Arg-specific proteases. The RgpB mutants produced were Y674F, Y674F Y718F, T675Q S679Q T682Q T684Q, T693Q, F695A, D696A, N698A, G699P, G716P, T724Q, T728Q T730Q, and K732Q and a protein with a deletion of residues 692 to 702 (Delta692-702). The mutants were characterized for cell-associated Arg-specific protease activity and for cellular distribution using anti-Rgp antibodies and Western blotting of culture fractions. All the mutants exhibited cell-associated Arg-specific activity similar to that of the positive control except for the D696A and Delta692-702 mutants. For all mutants, except D696A and Delta692-702, the RgpB proteins were found modified and attached to the cell surface, which was the same profile found in the positive-control strain. Only trace amounts of the precursor form of the Delta692-702 mutant were detected in the outer membrane, with none detected in the periplasm or culture fluid although cell transcript levels were normal. The results suggest that residues 692 to 702 of the CTD, in particular, residue D696, have an important role in the attachment of RgpB at the cell surface and that without attachment secretion does not occur.
21131497
Flavobacterium johnsoniae sprB is part of an operon spanning the additional gliding motility genes sprC, sprD, and sprF.
Cells of Flavobacterium johnsoniae move rapidly over surfaces by a process known as gliding motility. Gld proteins are thought to comprise the gliding motor that propels cell surface adhesins, such as the 669-kDa SprB. A novel protein secretion apparatus called the Por secretion system (PorSS) is required for assembly of SprB on the cell surface. Genetic and molecular analyses revealed that sprB is part of a seven-gene operon spanning 29.3 kbp of DNA. In addition to sprB, three other genes of this operon (sprC, sprD, and sprF) are involved in gliding. Mutations in sprB, sprC, sprD, and sprF resulted in cells that failed to form spreading colonies on agar but that exhibited some motility on glass in wet mounts. SprF exhibits some similarity to Porphyromonas gingivalis PorP, which is required for secretion of gingipain protease virulence factors via the P. gingivalis PorSS. F. johnsoniae sprF mutants produced SprB protein but were defective in localization of SprB to the cell surface, suggesting a role for SprF in secretion of SprB. The F. johnsoniae PorSS is involved in secretion of extracellular chitinase in addition to its role in secretion of SprB. SprF was not needed for chitinase secretion and may be specifically required for SprB secretion by the PorSS. Cells with nonpolar mutations in sprC or sprD produced and secreted SprB and propelled it rapidly along the cell surface. Multiple paralogs of sprB, sprC, sprD, and sprF are present in the genome, which may explain why mutations in sprB, sprC, sprD, and sprF do not result in complete loss of motility and suggests the possibility that semiredundant SprB-like adhesins may allow movement of cells over different surfaces.