In eukaryotes, the Nascent polypeptide-Associated Complex (NAC) is a heterodimeric cytosolic protein complex composed of NAC alpha (NACA) and NAC beta (BTF3) []. NAC binds reversibly to the ribosome where it is in contact with nascent chains as they emerge from the ribosome. But the cellular function of NAC seems to be much more diverse as it is also involved in transcription regulation and mitochondrial translocation [, ]. Alpha and beta NACs share homology with each other, both contain a NAC A/B domain. In archaea no beta NAC proteins are found; the complex is an homodimer of NAC alpha [, ].The crystal structure of an archeal NAC has been solved []. The NAC A/B domain consists of six strands arranged in a beta barrel structure similar to the OB fold. Various OB folds interact with ribosomal RNA which could suggest a similar role for the NAC A/B domain.This entry represents the mammalian transcription factor BTF3, which is a component of the nascent polypeptide-associated complex (NAC) []. In yeast, this component is known as nascent polypeptide-associated complex subunit beta-1 (or EGD1) [].
