A partial recombinant protein corresponding to amino acids 12-152 from the human protein was used as the immunogen for the FNDC5 antibody.
Irisin, also called Fibronectin type III domain-containing protein 5, is a secreted protein that is released from muscle cells during exercise. The encoded protein may participate in the development of brown fat. Translation of the precursor protein initiates at a non-AUG start codon at a position that is conserved as an AUG start codon in other organisms.