CK3, or Keratin 3, type II, is a human gene encoded by KRT3. It may also be known as: Keratin, type II cytoskeletal 3; 65 kDa cytokeratin; Cytokeratin-3; CK-3; Keratin-3; Type-II keratin Kb3; cytokeratin 3; K3. The encoded protein has an amino acid length of 628 and a mass of 64.4 kDa. CK3 is a member of the Intermediate filament family. Homologs of this gene exist in other organisms, including: Chicken.