SRPRB

SRPRB, or signal recognition particle receptor subunit beta, is a protein that forms part of the signal recognition particle (SRP) receptor in the endoplasmic reticulum. It assembles with the SRP receptor alpha subunit (SRPR) to create a functional receptor complex that captures ribosome-nascent chain complexes bearing signal sequences or translocating membrane proteins, guiding them to the ER membrane for insertion or translocation.

The SRP receptor operates at the surface of the endoplasmic reticulum. SRPRB participates in forming the heterodimeric receptor together with SRPR, and the complex coordinates the handover of the translating ribosome to the Sec61 translocon. This process is part of the co-translational targeting pathway that ensures secreted and membrane proteins are properly directed into or across the ER membrane.

In terms of structure and localization, SRPRB is considered a peripheral or membrane-associated subunit of the SRP receptor, contributing to the receptor’s membrane anchoring and interaction with SRPR. The beta subunit modulates the receptor’s activity during SRP-dependent docking and is involved in efficient engagement with the ribosome-nascent chain complex.

Genetically, the SRPRB gene is conserved across many eukaryotes and encodes one component of the SRP receptor complex. The protein participates in interactions with SRPR and other components of the SRP pathway as part of the broader protein targeting machinery that routes nascent polypeptides to the endoplasmic reticulum.