Translocation protein SEC63 homolog (SEC63)

Mediates cotranslational and post-translational transport of specific precursor polypeptides across endoplasmic reticulum (ER) (PubMed:22375059, PubMed:29719251). Proposed to play an auxiliary role in recognition of precursors with brief and apolar signal peptides.

May collaborate with SEC62 and HSPA5/BiP to facilitate targeting of small presecretory proteins to the SEC61 channel-forming translocon complex, triggering channel opening for polypeptide translocation into the ER lumen (PubMed:29719251). Required for efficient PKD1/Polycystin-1 biogenesis and trafficking to the plasma membrane of the principal cilia (By similarity).