Signal recognition particle receptor-β (SR-β) coordinates cotranslational N-glycosylation

Abstract

Proteins destined for the secretory compartment of the cell are cotranslationally translocated into the endoplasmic reticulum. The majority of these proteins are N-glycosylated, a co- and posttranslational modification that ensures proper protein folding, stability, solubility, and cellular localization. Here, we show that the β subunit of the signal recognition particle receptor (SR) is required for assembly of the N-glycosylation–competent translocon. We report that guanine analog chemical probes identified by high-throughput screening or mutation of the SR-β guanosine triphosphate binding site cause an N-glycosylation–deficient phenotype. Neither method alters the association of SR-α with SR-β, but both approaches reduce the association of SR-β with the oligosaccharyltransferase complex. These experiments demonstrate that SR-β has a previously unrecognized function coordinating endoplasmic reticulum translation with N-glycosylation.