Tyrosine kinase 2 regulatory pseudokinase domain (TYK2 JH2) (TYK2 JH2)

The Tyrosine kinase 2 (TYK2) regulatory pseudokinase domain, commonly referred to as the JH2 domain, is a non-catalytic structural region of the TYK2 protein that plays a pivotal role in regulating the enzyme's kinase activity (Source: UniProt P29597). While it lacks the ability to transfer phosphate groups, the JH2 domain functions as an allosteric switch that maintains the adjacent JH1 catalytic domain in an inactive state through an autoinhibitory interaction (Source: PubMed PMID: 30951666). TYK2 is a member of the Janus kinase (JAK) family and is essential for the signaling of cytokines such as Type I interferons, IL-12, and IL-23, which are central to the pathogenesis of various autoimmune and inflammatory diseases (Source: NIH/NCBI). Dysregulation of TYK2 signaling is strongly associated with conditions like psoriasis, psoriatic arthritis, and systemic lupus erythematosus (Source: PubMed PMID: 32833500). Unlike traditional JAK inhibitors that target the highly conserved ATP-binding site of the JH1 domain, novel therapeutics like deucravacitinib specifically bind to the JH2 domain. This allosteric binding stabilizes the autoinhibitory conformation, providing high selectivity for TYK2 over JAK1, JAK2, and JAK3 (Source: FDA Label for Sotyktu). This selectivity is clinically significant as it avoids the hematological and metabolic side effects, such as anemia and lipid changes, often seen with pan-JAK inhibitors (Source: StatPearls).

Other names

JH2 domainPseudokinase domain of TYK2Janus kinase 2-homology domainTYK2 JH2

Allosteric inhibition; the drug binds to the JH2 pseudokinase domain, inducing a conformational change that stabilizes the autoinhibitory interaction with the JH1 catalytic domain, thereby preventing kinase activation and downstream STAT phosphorylation (Source: PubMed PMID: 30951666).