Furukawa Arata, Yoshikaie Kunihito, Mori Takaharu, Mori Hiroyuki, Morimoto Yusuke V, Sugano Yasunori, Iwaki Shigehiro, Minamino Tohru, Sugita Yuji, Tanaka Yoshiki, Tsukazaki Tomoya
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan.
Theoretical Molecular Science Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
Cell Rep. 2017 May 2;19(5):895-901. doi: 10.1016/j.celrep.2017.04.030.
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.
由SecYEG转运体和SecA ATP酶介导的蛋白质分泌通过膜嵌入的SecDF利用质子动力得以增强。先前对SecDF的结构研究表明，它由12个可传导质子的跨膜螺旋和三个周质结构域组成，这些结构域形成至少两个特征性的过渡态，称为F型和I型。我们报告了处于I型的全长SecDF在2.6至2.8埃分辨率下的结构。这些结构显示，I型SecDF可生成一个穿透跨膜区域的通道，并作为由跨膜区域保守天冬氨酸残基调控的质子通路发挥作用。在一个晶体结构中，周质腔与一个分子相互作用，该分子可能是聚乙二醇，它可能模拟底物肽。这项研究为Sec蛋白转运提供了结构见解，有助于未来分析建立更详细的SecDF工作模型。
