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

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-resolu...

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Published in:Scientific reports 2016-12, Vol.6 (1), p.38399-38399, Article 38399
Main Authors: Botte, Mathieu, Zaccai, Nathan R, Nijeholt, Jelger Lycklama À, Martin, Remy, Knoops, Kèvin, Papai, Gabor, Zou, Juan, Deniaud, Aurélien, Karuppasamy, Manikandan, Jiang, Qiyang, Roy, Abhishek Singha, Schulten, Klaus, Schultz, Patrick, Rappsilber, Juri, Zaccai, Giuseppe, Berger, Imre, Collinson, Ian, Schaffitzel, Christiane
Format: Article
Language:English
Subjects:
Binding Sites
Biochemistry, Molecular Biology
Cloning, Molecular
Cryoelectron Microscopy
Electron microscopy
Escherichia coli - chemistry
Escherichia coli - genetics
Escherichia coli - metabolism
Escherichia coli Proteins - chemistry
Escherichia coli Proteins - genetics
Escherichia coli Proteins - metabolism
Gene Expression
Genetic Vectors - chemistry
Genetic Vectors - metabolism
Life Sciences
Lipids
Membrane proteins
Membrane Transport Proteins - chemistry
Membrane Transport Proteins - genetics
Membrane Transport Proteins - metabolism
Methanocaldococcus - chemistry
Methanocaldococcus - genetics
Methanocaldococcus - metabolism
Models, Molecular
Neutron Diffraction
Neutron scattering
Protein Binding
Protein Conformation, alpha-Helical
Protein Conformation, beta-Strand
Protein Interaction Domains and Motifs
Protein Transport
Proteins
Proteolysis
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
Recombinant Proteins - metabolism
Scattering, Small Angle
SEC Translocation Channels - chemistry
SEC Translocation Channels - genetics
SEC Translocation Channels - metabolism
Secretion
Structural Biology
Structural Homology, Protein
Substrate Specificity
Thermus thermophilus - chemistry
Thermus thermophilus - genetics
Thermus thermophilus - metabolism
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Summary: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.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep38399