Cytochrome b5 is a membrane-bound hemoprotein functioning as an electron carrier for several membrane-bound oxygenases. Component of a complex composed of cytochrome b5, NADH-cytochrome b5 reductase (CYB5R3) and MTARC2. Belongs to the cytochrome b5 family. It is uncertain whether Met-1 or Met-5 is the initiator. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.