ジャーナル: Elife / 年: 2017 タイトル: Cryo-EM structure of the bifunctional secretin complex of . 著者: Edoardo D'Imprima / Ralf Salzer / Ramachandra M Bhaskara / Ricardo Sánchez / Ilona Rose / Lennart Kirchner / Gerhard Hummer / Werner Kühlbrandt / Janet Vonck / Beate Averhoff / 要旨: 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 is an ...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 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.
タイプ: PROJECTION MATCHING / ソフトウェア - 名称: FREALIGN 詳細: The images of the subdomain containing the N2 and N3 rings after residual signal subtraction were recentered and placed in a smaller with our new program REP, followed by refinement by FREALIGN.