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Cryo-EM structure of the bifunctional secretin complex of Thermus thermophilus.

ABSTRACT: Secretins form multimeric channels across the outer membrane of Gram-negative bacteria that mediate the import or export of substrates and/or extrusion of type IV pili. The secretin complex of Thermus thermophilus is an oligomer of the 757-residue PilQ protein, essential for DNA uptake and pilus extrusion. Here, we present the cryo-EM structure of this bifunctional complex at a resolution of ~7 Å using a new reconstruction protocol. Thirteen protomers form a large periplasmic domain of six stacked rings and a secretin domain in the outer membrane. A homology model of the PilQ protein was fitted into the cryo-EM map. A crown-like structure outside the outer membrane capping the secretin was found not to be part of PilQ. Mutations in the secretin domain disrupted the crown and abolished DNA uptake, suggesting a central role of the crown in natural transformation.

SUBMITTER: D'Imprima E

PROVIDER: S-EPMC5745081 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Cryo-EM structure of the bifunctional secretin complex of <i>Thermus thermophilus</i>.

D'Imprima Edoardo E Salzer Ralf R Bhaskara Ramachandra M RM Sánchez Ricardo R Rose Ilona I Kirchner Lennart L Hummer Gerhard G Kühlbrandt Werner W Vonck Janet J Averhoff Beate B

eLife 20171227

Secretins form multimeric channels across the outer membrane of Gram-negative bacteria that mediate the import or export of substrates and/or extrusion of type IV pili. The secretin complex of <i>Thermus thermophilus</i> is an oligomer of the 757-residue PilQ protein, essential for DNA uptake and pilus extrusion. Here, we present the cryo-EM structure of this bifunctional complex at a resolution of ~7 Å using a new reconstruction protocol. Thirteen protomers form a large periplasmic domain of si ...[more]

PMID: 29280731

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