The Get1/2 insertase forms a channel to mediate the insertion of tail-anchored proteins into the ER

Cell Rep. 2023 Jan 31;42(1):111921. doi: 10.1016/j.celrep.2022.111921. Epub 2022 Dec 28.

Abstract

Tail-anchored (TA) proteins contain a single C-terminal transmembrane domain (TMD) that is captured by the cytosolic Get3 in yeast (TRC40 in humans). Get3 delivers TA proteins to the Get1/2 complex for insertion into the endoplasmic reticulum (ER) membrane. How Get1/2 mediates insertion of TMDs of TA proteins into the membrane is poorly understood. Using bulk fluorescence and microfluidics assays, we show that Get1/2 forms an aqueous channel in reconstituted bilayers. We estimate the channel diameter to be ∼2.5 nm wide, corresponding to the circumference of two Get1/2 complexes. We find that the Get3 binding can seal the Get1/2 channel, which dynamically opens and closes. Our mutation analysis further shows that the Get1/2 channel activity is required to release TA proteins from Get3 for insertion into the membrane. Hence, we propose that the Get1/2 channel functions as an insertase for insertion of TMDs and as a translocase for translocation of C-terminal hydrophilic segments.

Keywords: CP: Cell biology; CP: Molecular biology; channel; membrane protein insertion; protein translocation; tail-anchored proteins.

Publication types

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

MeSH terms

  • Endoplasmic Reticulum / metabolism
  • Guanine Nucleotide Exchange Factors / metabolism
  • Humans
  • Membrane Proteins / metabolism
  • Protein Transport
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins* / metabolism

Substances

  • Saccharomyces cerevisiae Proteins
  • Membrane Proteins
  • Guanine Nucleotide Exchange Factors
  • GET1 protein, S cerevisiae