SRP keeps polypeptides translocation-competent by slowing translation to match limiting ER-targeting sites.

ABSTRACT: SRP is essential for targeting nascent chains to the endoplasmic reticulum, and it delays nascent chain elongation in cell-free translation systems. However, the significance of this function has remained unclear. We show that efficient protein translocation into the ER is incompatible with normal cellular translation rates due to rate-limiting concentrations of SRP receptor (SR). We complemented mammalian cells depleted of SRP14 by expressing mutant versions of the protein lacking the elongation arrest function. The absence of a delay caused inefficient targeting of preproteins leading to defects in secretion, depletion of proteins in the endogenous membranes, and reduced cell growth. The detrimental effects were reversed by either reducing the cellular protein synthesis rate or increasin

SUBMITTER: Lakkaraju AK 

PROVIDER: S-EPMC2430734 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature