A central cavity within the holo-translocon suggests a mechanism for membrane protein insertion

Mathieu Botte, Nathan Zaccai, Jelger Lycklama a Nijeholt, Remy Martin, Kevin Knoops, Gabor Papai, Juan Zou, Aurelien Deniaud, Manikandan Karuppasamy, Qiyang Jiang, Abhishek Singha Roy, Klaus Schulten, Patrick Schultz, Juri Rappsilber

Research output: Contribution to journalArticlepeer-review

Abstract

The conserved SecYEG protein-conducting channel and the accessory proteins SecDF-YajC and YidC constitute the bacterial holo-translocon (HTL), capable of protein-secretion and membrane-protein insertion. By employing an integrative approach combining small-angle neutron scattering (SANS), low-resolution electron microscopy and biophysical analyses we determined the arrangement of the proteins and lipids within the supercomplex. The results guided the placement of X-ray structures of individual HTL components and allowed the proposal of a model of the functional translocon. Their arrangement around a central lipid-containing pool conveys an unexpected, but compelling mechanism for membrane-protein insertion. The periplasmic domains of YidC and SecD are poised at the protein-channel exit-site of SecY, presumably to aid the emergence of translocating polypeptides. The SecY lateral gate for membrane-insertion is adjacent to the membrane ‘insertase’ YidC. Absolute-scale SANS employing a novel contrast-match-point analysis revealed a dynamic complex adopting open and compact configurations around an adaptable central lipid-filled chamber, wherein polytopic membrane-proteins could fold, sheltered from aggregation and proteolysis.

Original languageEnglish
Article number38399
JournalScientific Reports
Early online date7 Dec 2016
DOIs
Publication statusE-pub ahead of print - 7 Dec 2016

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