1. Tunnel Formation Inferred from the I -Form Structures of the Proton-Driven Protein Secretion Motor SecDF
- Author
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Furukawa, Arata, Yoshikaie, Kunihito, Mori, Takaharu, Mori, Hiroyuki, Morimoto, Yusuke V., Sugano, Yasunori, Iwaki, Shigehiro, Minamino, Tohru, Sugita, Yuji, Tanaka, Yoshiki, and Tsukazaki, Tomoya
- Subjects
crystal structure ,protein translocation ,SecYEG ,SecDF ,Sec proteins ,membrane protein - 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-Å 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.
- Published
- 2017