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The outer membrane protein LptO is essential for the O‐deacylation of LPS and the co‐ordinated secretion and attachment of A‐LPS and CTD proteins in Porphyromonas gingivalis
Author(s) -
Chen YuYen,
Peng Benjamin,
Yang Qiaohui,
Glew Michelle D.,
Veith Paul D.,
Cross Keith J.,
Goldie Kenneth N.,
Chen Dina,
O'BrienSimpson Neil,
Dashper Stuart G,
Reynolds Eric C.
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07530.x
Subject(s) - secretion , bacterial outer membrane , porphyromonas gingivalis , periplasmic space , biology , mutant , phosphorylation , secretory protein , biochemistry , microbiology and biotechnology , membrane protein , membrane , bacteria , escherichia coli , genetics , gene
Summary Protein substrates of a novel secretion system of Porphyromonas gingivalis contain a conserved C‐terminal domain (CTD) essential for secretion and attachment to the cell surface. Inactivation of lptO (PG0027) or porT produced mutants that lacked surface protease activity and an electron‐dense surface layer. Both mutants showed co‐accumulation of A‐LPS and unmodified CTD proteins in the periplasm. Lipid profiling by mass spectrometry showed the presence of both tetra‐ and penta‐acylated forms of mono‐phosphorylated lipid A in the wild‐type and porT mutant, while only the penta‐acylated forms of mono‐phosphorylated lipid A were found in the lptO mutant, indicating a specific role of LptO in the O‐deacylation of mono‐phosphorylated lipid A. Increased levels of non‐phosphorylated lipid A and the presence of novel phospholipids in the lptO mutant were also observed that may compensate for the missing mono‐phosphorylated tetra‐acylated lipid A in the outer membrane (OM). Molecular modelling predicted LptO to adopt a β‐barrel structure characteristic of an OM protein, supported by the enrichment of LptO in OM vesicles. The results suggest that LPS deacylation by LptO is linked to the co‐ordinated secretion of A‐LPS and CTD proteins by a novel secretion and attachment system to form a structured surface layer.