Co-translational targeting and translocation of proteins to the endoplasmic reticulum

Abstract

Co-translational protein targeting to the endoplasmic reticulum (ER), represents an evolutionary-conserved mechanism to target proteins into the secretory pathway. In this targeting pathway proteins possessing signal sequences are recognised at the ribosome by the signal recognition particle while they are still undergoing synthesis. This triggers their delivery to the ER protein translocation channel, where they are directly translocated into the ER. Here we review the current understanding of this translocation pathway and how molecular details obtained in the related bacterial system have provided insight into the mechanism of targeting and translocation. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.

Keywords: 5′-guanylyl imidodiphosphate; BiP; ER; GppNHp; OST; Protein biogenesis; Protein targeting; Protein translocation; RAMP4; RNC; Ribosome; SPase; SR; SRP; Signal recognition particle; TM; TRAM; TRAP; Translocon; binding immunoglobulin protein; endoplasmic reticulum; oligosaccharyl transferase; rRNA; ribosomal RNA; ribosome nascent chain complex; ribosome-associated membrane protein 4; ribosome-nascent chain complex; signal peptidase; signal recognition particle; signal recognition particle receptor; tRNA; transfer RNA; translocating chain-associated membrane protein; translocon-associated protein complex; transmembrane helix.