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Nat Struct Mol Biol. 2015 Jul;22(7):540-6. doi: 10.1038/nsmb.3044. Epub 2015 Jun 8.

The pilus usher controls protein interactions via domain masking and is functional as an oligomer.

Author information

1
1] Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA. [2] Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA.
2
1] Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA. [2] Biosciences Department, Brookhaven National Laboratory, Upton, New York, USA.
3
1] Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri, USA. [2] Center for Women's Infectious Disease Research, Washington University School of Medicine, Saint Louis, Missouri, USA.

Abstract

The chaperone-usher (CU) pathway assembles organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Biogenesis of pili by the CU pathway requires a periplasmic chaperone and an outer-membrane protein termed the usher (FimD). We show that the FimD C-terminal domains provide the high-affinity substrate-binding site but that these domains are masked in the resting usher. Domain masking requires the FimD plug domain, which serves as a switch controlling usher activation. We demonstrate that usher molecules can act in trans for pilus biogenesis, providing conclusive evidence for a functional usher oligomer. These results reveal mechanisms by which molecular machines such as the usher regulate and harness protein-protein interactions and suggest that ushers may interact in a cooperative manner during pilus assembly in bacteria.

PMID:
26052892
PMCID:
PMC4496297
DOI:
10.1038/nsmb.3044
[Indexed for MEDLINE]
Free PMC Article

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