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Ramifications of kinetic partitioning on usher‐mediated pilus biogenesis
Author(s) -
Saulino E. T.,
Thanassi D. G.,
Pinkner J. S.,
Hultgren S. J.
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.8.2177
Subject(s) - chaperone (clinical) , pilus , bacterial adhesin , biology , biogenesis , microbiology and biotechnology , protein subunit , plasma protein binding , biochemistry , escherichia coli , gene , medicine , pathology
The biogenesis of diverse adhesive structures in a variety of Gram‐negative bacterial species is dependent on the chaperone/usher pathway. Very little is known about how the usher protein translocates protein subunits across the outer membrane or how assembly of these adhesive structures occurs. We have discovered several mechanisms by which the usher protein acts to regulate the ordered assembly of type 1 pili, specifically through critical interactions of the chaperone–adhesin complex with the usher. A study of association and dissociation events of chaperone–subunit complexes with the usher in real time using surface plasmon resonance revealed that the chaperone–adhesin complex has the tightest and fastest association with the usher. This suggests that kinetic partitioning of chaperone–adhesin complexes to the usher is a defining factor in tip localization of the adhesin in the pilus. Furthermore, we identified and purified a chaperone–adhesin–usher assembly intermediate that was formed in vivo . Trypsin digestion assays showed that the usher in this complex was in an altered conformation, which was maintained during pilus assembly. The data support a model in which binding of the chaperone–adhesin complex to the usher stabilizes the usher in an assembly‐competent conformation and allows initiation of pilus assembly.