Nascent Polypeptide Associated Complex Alpha 1 (NACa1)

Wiedmann et al. (1994) purified the heterodimeric nascent polypeptide-associated complex (NAC) from bovine cytosol and determined that it contains Naca, which migrated at an apparent molecular mass of about 33 kD, and Btf3b, which migrated at an apparent molecular mass of about 21 kD. Using peptide sequences from the purified proteins, they cloned human NACA and BTF3B.

NAC did not bind to fully emerged signal peptides. In the absence of NAC, the signal recognition particle (SRP) interacted with polypeptides even in the absence of a signal peptide and allowed mistargeting of the protein to the SRP receptor at the endoplasmic reticulum membrane. Readdition of purified NAC prevented mistranslocation.