This domain is found in Protein translocase subunit SecDF from Thermus thermophilus, which belongs to the RND superfamily. SecDF shows 12 transmembrane (TM) regions and 6 periplasmic regions (P1-P6). This entry represents the N-terminal region of the base subdomain of the P1 domain that is located in the N- terminal half of the polypeptide, also known as SecD region. This domain folds into a a pseudo-symmetrical anti-parallel beta-sheet that rearranges to a beta-barrel architecture during ion transport. This domain, which covers the TM region [1-4], is related to Pfam:PF03176 and usually appears associated with Pfam:PF07549 and Pfam:PF02355.

1: Structure and function of a membrane component SecDF that enhances protein export. Tsukazaki T, Mori H, Echizen Y, Ishitani R, Fukai S, Tanaka T, Perederina A, Vassylyev DG, Kohno T, Maturana AD, Ito K, Nureki O; Nature. 2011;474:235-238. PMID:21562494

2: A central cavity within the holo-translocon suggests a mechanism for membrane protein insertion. Botte M, Zaccai NR, Nijeholt JL, Martin R, Knoops K, Papai G, Zou J, Deniaud A, Karuppasamy M, Jiang Q, Roy AS, Schulten K, Schultz P, Rappsilber J, Zaccai G, Berger I, Collinson I, Schaffitzel C; Sci Rep. 2016;6:38399. PMID:27924919

3: Tunnel Formation Inferred from the I-Form Structures of the Proton-Driven Protein Secretion Motor SecDF. Furukawa A, Yoshikaie K, Mori T, Mori H, Morimoto YV, Sugano Y, Iwaki S, Minamino T, Sugita Y, Tanaka Y, Tsukazaki T; Cell Rep. 2017;19:895-901. PMID:28467902

4: Remote Coupled Drastic beta-Barrel to beta-Sheet Transition of the Protein Translocation Motor. Furukawa A, Nakayama S, Yoshikaie K, Tanaka Y, Tsukazaki T; Structure. 2018;26:485-489. PMID:29398525