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Publication - Professor Christiane Berger-Schaffitzel

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


    Botte, M, Zaccai, NR, Nijeholt, JL&#x, Ma;rtin, 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, 2016, ‘A central cavity within the holo-translocon suggests a mechanism for membrane protein insertion’. Scientific Reports, vol 6.


    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 super-complex. 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.

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