Chaperone (clinical)

Biology

Cytosol

Gene

Biophysics

Endoplasmic reticulum

Peptide sequence

Transmembrane protein

Protein targeting

Cell biology

Medicine

Biochemistry

Signal peptide

Membrane protein

Sec61

Chromosomal translocation

Receptor

Enzyme

Membrane

Transport protein

Ribosome

Pathology

Translocon

Annual Review of Cell and Developmental Biology

Many proteins are translocated across the endoplasmic reticulum (ER) membrane in eukaryotes or the plasma membrane in prokaryotes. These proteins use hydrophobic signal sequences or transmembrane (TM) segments to trigger their translocation through the protein-conducting Sec61/SecY channel. Substrates are first directed to the channel by cytosolic targeting factors, which use hydrophobic pockets to bind diverse signal and TM sequences. Subsequently, these hydrophobic sequences insert into the channel, docking into a groove on the outside of the lateral gate of the channel, where they also interact with lipids. Structural data and biochemical experiments have elucidated how channel partners, the ribosome in cotranslational translocation, and the eukaryotic ER chaperone BiP or the prokaryotic cytosolic SecA ATPase in posttranslational translocation move polypeptides unidirectionally across the membrane. Structures of auxiliary components of the bacterial translocon, YidC and SecD/F, provide additional insight. ...

Structural and Mechanistic Insights into Protein Translocation