PMID: 28467902

Authors:

Furukawa A, Yoshikaie K, Mori T, Mori H, Morimoto YV, Sugano Y, Iwaki S, Minamino T, Sugita Y, Tanaka Y, Tsukazaki T

Title:

Tunnel Formation Inferred from the I-Form Structures of the Proton-Driven Protein Secretion Motor SecDF.

Journal:

Cell Rep. 2017 May 2;19(5):895-901. doi: 10.1016/j.celrep.2017.04.030.

Abstract:

Protein secretion mediated by SecYEG translocon and SecA ATPase is enhanced by membrane-embedded SecDF by using proton motive force. A previous structural study of SecDF indicated that it comprises 12 transmembrane helices that can conduct protons and three periplasmic domains, which form at least two characterized transition states, termed the F and I forms. We report the structures of full-length SecDF in I form at 2.6- to 2.8-A resolution. The structures revealed that SecDF in I form can generate a tunnel that penetrates the transmembrane region and functions as a proton pathway regulated by a conserved Asp residue of the transmembrane region. In one crystal structure, periplasmic cavity interacts with a molecule, potentially polyethylene glycol, which may mimic a substrate peptide. This study provides structural insights into the Sec protein translocation that allows future analyses to develop a more detailed working model for SecDF.