Schematic representation of PERK and all mutations reported to date. PERK is composed of a signal peptide (sp), followed by a regulatory domain and a catalytic domain that contains two serine-threonine kinase domains (orange bars). PEK mutations that result in missense mutations are all located within or in the near vicinity of kinase domains (orange blocks). Nonsense (X) and frameshift (FS) mutations, that result in truncated proteins are represented below, and are spread over the length of the protein. Mutations that were found as compound heterozygous in WRS patients are labelled with a "(c)", all others were found in the homozygous state in WRS patients. Mutations homozygous in patients with a relatively late diabetes onset (14 and 30 months) are noted by "(1)" and those homozygous in patients with a relatively longer survival (32 and 35 years) are noted by "(2)". Two mutations were splice mutations located in intron and are not represented. PERK sequence and the position of mutations are provided relative to NCBI RefSeq (NP_004827).