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Mechanism of fibre assembly through the chaperone–usher pathway
Author(s) -
Vetsch Michael,
Erilov Denis,
Molière Noël,
Nishiyama Mireille,
Ignatov Oleksandr,
Glockshuber Rudi
Publication year - 2006
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/sj.embor.7400722
Subject(s) - chaperone (clinical) , protein subunit , periplasmic space , pilus , microbiology and biotechnology , chemistry , biophysics , biology , biochemistry , escherichia coli , gene , medicine , pathology
The chaperone–usher pathway directs the formation of adhesive surface fibres in numerous pathogenic Gram‐negative bacteria. The fibres or pili consist exclusively of protein subunits that, before assembly, form transient complexes with a chaperone in the periplasm. In these chaperone:subunit complexes, the chaperone donates one β‐strand to complete the imperfect immunoglobulin‐like fold of the subunit. During pilus assembly, the chaperone is replaced by a polypeptide extension of another subunit in a process termed ‘donor strand exchange’ (DSE). Here we show that DSE occurs in a concerted reaction in which a chaperone‐bound acceptor subunit is attacked by another chaperone‐bound donor subunit. We provide evidence that efficient DSE requires interactions between the reacting subunits in addition to those involving the attacking donor strand. Our results indicate that the pilus assembly platforms in the outer membrane, referred to as ushers, catalyse fibre formation by increasing the effective concentrations of donor and acceptor subunits.