Dissecting the molecular organization of the translocon-associated protein complex

Nat Commun. 2017 Feb 20;8:14516. doi: 10.1038/ncomms14516.

Abstract

In eukaryotic cells, one-third of all proteins must be transported across or inserted into the endoplasmic reticulum (ER) membrane by the ER protein translocon. The translocon-associated protein (TRAP) complex is an integral component of the translocon, assisting the Sec61 protein-conducting channel by regulating signal sequence and transmembrane helix insertion in a substrate-dependent manner. Here we use cryo-electron tomography (CET) to study the structure of the native translocon in evolutionarily divergent organisms and disease-linked TRAP mutant fibroblasts from human patients. The structural differences detected by subtomogram analysis form a basis for dissecting the molecular organization of the TRAP complex. We assign positions to the four TRAP subunits within the complex, providing insights into their individual functions. The revealed molecular architecture of a central translocon component advances our understanding of membrane protein biogenesis and sheds light on the role of TRAP in human congenital disorders of glycosylation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Binding Proteins / chemistry
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Cells, Cultured
  • Cryoelectron Microscopy / methods
  • Electron Microscope Tomography / methods
  • Endoplasmic Reticulum / metabolism
  • Fibroblasts / metabolism
  • Glycosylation
  • HeLa Cells
  • Humans
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Models, Molecular
  • Multiprotein Complexes / chemistry
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Mutation
  • Protein Conformation
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Protein Transport
  • Receptors, Cytoplasmic and Nuclear / chemistry
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Receptors, Peptide / chemistry
  • Receptors, Peptide / genetics
  • Receptors, Peptide / metabolism*
  • SEC Translocation Channels / chemistry
  • SEC Translocation Channels / metabolism

Substances

  • Calcium-Binding Proteins
  • Membrane Glycoproteins
  • Multiprotein Complexes
  • Protein Subunits
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Peptide
  • SEC Translocation Channels
  • signal sequence receptor