intracellular protein transmembrane transport / SRP-dependent cotranslational protein targeting to membrane, translocation / signal sequence binding / protein secretion / protein transmembrane transporter activity / protein targeting / protein transport / plasma membrane 類似検索 - 分子機能
Preprotein translocase subunit SecG / Protein translocase subunit SecY / Protein transport protein SecG/Sec61-beta/Sbh / Sec61beta family / Protein translocase SEC61 complex, gamma subunit / Protein translocase SecE domain superfamily / Translocon Sec61/SecY, plug domain / Plug domain of Sec61p / Protein secY signature 1. / Protein secY signature 2. ...Preprotein translocase subunit SecG / Protein translocase subunit SecY / Protein transport protein SecG/Sec61-beta/Sbh / Sec61beta family / Protein translocase SEC61 complex, gamma subunit / Protein translocase SecE domain superfamily / Translocon Sec61/SecY, plug domain / Plug domain of Sec61p / Protein secY signature 1. / Protein secY signature 2. / SecE/Sec61-gamma subunits of protein translocation complex / Protein translocase complex, SecE/Sec61-gamma subunit / SecY/SEC61-alpha family / SecY domain superfamily / SecY conserved site / SecY 類似検索 - ドメイン・相同性
Preprotein translocase subunit SecG / Protein translocase subunit SecE / Protein translocase subunit SecY 類似検索 - 構成要素
ジャーナル: Nature / 年: 2014 タイトル: Structure of the SecY channel during initiation of protein translocation. 著者: Eunyong Park / Jean-François Ménétret / James C Gumbart / Steven J Ludtke / Weikai Li / Andrew Whynot / Tom A Rapoport / Christopher W Akey / 要旨: Many secretory proteins are targeted by signal sequences to a protein-conducting channel, formed by prokaryotic SecY or eukaryotic Sec61 complexes, and are translocated across the membrane during ...Many secretory proteins are targeted by signal sequences to a protein-conducting channel, formed by prokaryotic SecY or eukaryotic Sec61 complexes, and are translocated across the membrane during their synthesis. Crystal structures of the inactive channel show that the SecY subunit of the heterotrimeric complex consists of two halves that form an hourglass-shaped pore with a constriction in the middle of the membrane and a lateral gate that faces the lipid phase. The closed channel has an empty cytoplasmic funnel and an extracellular funnel that is filled with a small helical domain, called the plug. During initiation of translocation, a ribosome-nascent chain complex binds to the SecY (or Sec61) complex, resulting in insertion of the nascent chain. However, the mechanism of channel opening during translocation is unclear. Here we have addressed this question by determining structures of inactive and active ribosome-channel complexes with cryo-electron microscopy. Non-translating ribosome-SecY channel complexes derived from Methanocaldococcus jannaschii or Escherichia coli show the channel in its closed state, and indicate that ribosome binding per se causes only minor changes. The structure of an active E. coli ribosome-channel complex demonstrates that the nascent chain opens the channel, causing mostly rigid body movements of the amino- and carboxy-terminal halves of SecY. In this early translocation intermediate, the polypeptide inserts as a loop into the SecY channel with the hydrophobic signal sequence intercalated into the open lateral gate. The nascent chain also forms a loop on the cytoplasmic surface of SecY rather than entering the channel directly.
名称: Methanococcus jannaschii 70S ribosome-SecYEbeta complex タイプ: sample / ID: 1000 詳細: The sample was reconstituted from ribosomal subunits purified from M. jannaschii and from recombinant SecYEbeta. 集合状態: one 70S, one E-site tRNA, one SecYEbeta channel Number unique components: 3
分子量
理論値: 2.6 MDa
-
超分子 #1: non-translating 70S ribosome
超分子
名称: non-translating 70S ribosome / タイプ: complex / ID: 1 / 組換発現: No / データベース: NCBI / Ribosome-details: ribosome-prokaryote: ALL
Particles were selected with e2boxer and CTF-corrected with EMAN2. Final maps were obtained from 6 different refinement conditions, aligned in Chimera, and averaged to produce the final map.
CTF補正
詳細: per micrograph
最終 再構成
アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 9.0 Å / 解像度の算出法: OTHER / ソフトウェア - 名称: EMAN1, EMAN2 詳細: Final map calculated as an average of 6 different refinements in EMAN2 with different parameters. 使用した粒子像数: 37000