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The S‐layer proteins of Tannerella forsythia are secreted via a type IX secretion system that is decoupled from protein O ‐glycosylation
Author(s) -
Tomek M.B.,
Neumann L.,
Nimeth I.,
Koerdt A.,
Andesner P.,
Messner P.,
Mach L.,
Potempa J.S.,
Schäffer C.
Publication year - 2014
Publication title -
molecular oral microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 77
eISSN - 2041-1014
pISSN - 2041-1006
DOI - 10.1111/omi.12062
Subject(s) - s layer , glycosylation , secretion , periplasmic space , mutant , microbiology and biotechnology , biology , biochemistry , chemistry , escherichia coli , gene
Summary Conserved C‐terminal domains ( CTD ) have been shown to act as a signal for the translocation of certain proteins across the outer membrane of Bacteroidetes via a type IX secretion system (T9 SS ). The genome sequence of the periodontal pathogen T annerella forsythia predicts the presence of the components for a T9 SS in conjunction with a suite of CTD proteins. T . forsythia is covered with a two‐dimensional crystalline surface (S‐) layer composed of the glycosylated CTD proteins TfsA and TfsB. To investigate, if T9 SS is functional in T . forsythia , T9 SS ‐deficient mutants were generated by targeting either TF 0955 (putative C‐terminal signal peptidase) or TF 2327 (PorK ortholog), and the mutants were analyzed with respect to secretion, assembly and glycosylation of the S‐layer proteins as well as proteolytic processing of the CTD and biofilm formation. In either mutant, TfsA and TfsB were incapable of translocation, as evidenced by the absence of the S‐layer in transmission electron microscopy of ultrathin‐sectioned bacterial cells. Despite being entrapped within the periplasm, mass spectrometry analysis revealed that the S‐layer proteins were modified with the complete, mature glycan found on the secreted proteins, indicating that protein translocation and glycosylation are two independent processes. Further, the T9 SS mutants showed a denser biofilm with fewer voids compared with the wild‐type. This study demonstrates the functionality of T9 SS and the requirement of CTD for the outer membrane passage of extracellular proteins in T. forsythia , exemplified by the two S‐layer proteins. In addition, T9 SS protein translocation is decoupled from O ‐glycan attachment in T. forsythia .