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Protein Substrates of a Novel Secretion System Are Numerous in the Bacteroidetes Phylum and Have in Common a Cleavable C‑Terminal Secretion Signal, Extensive Post-Translational Modification, and Cell-Surface Attachment
journal contribution
posted on 2013-10-04, 00:00 authored by Paul D. Veith, Nor A. Nor Muhammad, Stuart G. Dashper, Vladimir A. Likić, Dhana G. Gorasia, Dina Chen, Samantha J. Byrne, Deanne V. Catmull, Eric C. ReynoldsThe secretion of certain proteins
in Porphyromonas gingivalis is dependent on a C-terminal
domain (CTD). After secretion, the
CTD is cleaved prior to extensive modification of the mature protein,
probably with lipopolysaccharide, therefore enabling attachment to
the cell surface. In this study, bioinformatic analyses of the CTD
demonstrated the presence of three conserved sequence motifs. These
motifs were used to construct Hidden Markov Models (HMMs) that predicted
663 CTD-containing proteins in 21 fully sequenced species of the Bacteroidetes phylum, while no CTD-containing proteins were
predicted in species outside this phylum. Further HMM searching of Cytophaga hutchinsonii led to a total of 171 predicted CTD
proteins in that organism alone. Proteomic analyses of membrane fractions
and culture fluid derived from P. gingivalis and
four other species containing predicted CTDs (Parabacteroides
distasonis, Prevotella intermedia, Tannerella forsythia, and C. hutchinsonii) demonstrated that membrane localization, extensive post-translational
modification, and CTD-cleavage were conserved features of the secretion
system. The CTD cleavage site of 10 different proteins from 3 different
species was determined and found to be similar to the cleavage site
previously determined in P. gingivalis, suggesting
that homologues of the C-terminal signal peptidase (PG0026) are responsible
for the cleavage in these species.
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Novel Secretion SystemPrevotella intermediabioinformatic analysesBacteroidetes Phylumsecretion systemProtein SubstratesPorphyromonas gingivalisCTD cleavage siteParabacteroides distasonisMarkov ModelsHMMTannerella forsythiacleavage sitemembrane localizationPGsequence motifsCytophaga hutchinsoniiCTD proteinsProteomic analysesculture fluidBacteroidetes phylumcell surfacespeciesmembrane fractions