1.B.44 The Probable Protein Translocating Porphyromonas gingivalis Porin (PorT) Family
The Gram-negative priodontopathogenic bacterium, Porphyromonas gingivalis, secretes proteinases (gingipains) and adhesin complexes as virulence factors to the cell surface or external milieu. Mutants in the porT gene showed weak gingipain activities in cell lysates. The precursor forms of gingipains and the adhesins accumulated in the periplasm and lacked the N-terminal signal peptide regions. However, they were not further processed. The final processing steps are known to occur after passage of the proteins through the outer membrane on the cell surface. Products of the kgp, rgpA, rgpB and hagA genes are all apparently exported across the outer membrane via PorT. It is not known if other constituents play a role (Sato et al., 2005).
PorT has 244 aas, a strongly hydrophobic leader sequence (hydrophobic TMS at residues 9-27), and 8 amphipathic transmembrane β-strands (Nguyen et al., 2009). It is homologous throughout most of its length with a hypothetical protein (Chut02002746; BAA36600) from Cytophaga hutchinsonii (225 aas; 33% identity, 54% similarity; e-21).