6E15

Handover mechanism of the growing pilus by the bacterial outer membrane usher FimD

Summary for 6E15

• Entry DOI: 10.2210/pdb6e15/pdb
• EMDB information: 8954
• Descriptor: Chaperone protein FimC, Fimbrial biogenesis outer membrane usher protein, Protein FimF, ... (5 entities in total)
• Functional Keywords: pili, chaperone, usher, membrane protein
• Biological source: Escherichia coli; More
• Total number of polymer chains: 5
• Total formula weight: 187480.44

Authors

Du, M.,Yuan, Z.,Yu, H.,Henderson, N.,Sarowar, S.,Zhao, G.,Werneburg, G.T.,Thanassi, D.G.,Li, H. (deposition date: 2018-07-09, release date: 2018-10-17, Last modification date: 2025-06-04)

Primary citation

Du, M.,Yuan, Z.,Yu, H.,Henderson, N.,Sarowar, S.,Zhao, G.,Werneburg, G.T.,Thanassi, D.G.,Li, H.
Handover mechanism of the growing pilus by the bacterial outer-membrane usher FimD.
Nature, 562:444-447, 2018

PubMed Abstract: Pathogenic bacteria such as Escherichia coli assemble surface structures termed pili, or fimbriae, to mediate binding to host-cell receptors. Type 1 pili are assembled via the conserved chaperone-usher pathway. The outer-membrane usher FimD recruits pilus subunits bound by the chaperone FimC via the periplasmic N-terminal domain of the usher. Subunit translocation through the β-barrel channel of the usher occurs at the two C-terminal domains (which we label CTD1 and CTD2) of this protein. How the chaperone-subunit complex bound to the N-terminal domain is handed over to the C-terminal domains, as well as the timing of subunit polymerization into the growing pilus, have previously been unclear. Here we use cryo-electron microscopy to capture a pilus assembly intermediate (FimD-FimC-FimF-FimG-FimH) in a conformation in which FimD is in the process of handing over the chaperone-bound end of the growing pilus to the C-terminal domains. In this structure, FimF has already polymerized with FimG, and the N-terminal domain of FimD swings over to bind CTD2; the N-terminal domain maintains contact with FimC-FimF, while at the same time permitting access to the C-terminal domains. FimD has an intrinsically disordered N-terminal tail that precedes the N-terminal domain. This N-terminal tail folds into a helical motif upon recruiting the FimC-subunit complex, but reorganizes into a loop to bind CTD2 during handover. Because both the N-terminal and C-terminal domains of FimD are bound to the end of the growing pilus, the structure further suggests a mechanism for stabilizing the assembly intermediate to prevent the pilus fibre diffusing away during the incorporation of thousands of subunits.

PubMed: 30283140
DOI: 10.1038/s41586-018-0587-z

Experimental method

ELECTRON MICROSCOPY (5.1 Å)