Tyrosine kinase 2, Janus homology 2 (JH2) pseudokinase domain (TYK2 JH2)

The Tyrosine kinase 2 (TYK2) Janus homology 2 (JH2) pseudokinase domain is a critical regulatory region of the TYK2 protein, which belongs to the Janus kinase (JAK) family. Although it possesses a kinase-like fold, the JH2 domain is catalytically inactive and functions primarily to autoinhibit the adjacent JH1 catalytic domain. This domain has become a premier therapeutic target because its structure is significantly more distinct among JAK family members than the highly conserved JH1 ATP-binding sites, allowing for the development of highly selective allosteric inhibitors. By binding to the JH2 domain, drugs like deucravacitinib stabilize the enzyme's inactive conformation, effectively blocking the signaling of cytokines such as interleukin-12 (IL-12), interleukin-23 (IL-23), and Type I interferons. This selective inhibition is vital for treating autoimmune conditions like psoriasis, psoriatic arthritis, and systemic lupus erythematosus while avoiding the systemic toxicities—such as anemia and neutropenia—associated with non-selective JAK inhibitors. Consequently, the TYK2 JH2 domain represents a major advancement in precision medicine for inflammatory diseases.

Other names

TYK2 regulatory domainTYK2 pseudokinase domainJanus homology 2 domain of TYK2TYK2 JH2 domain

Allosteric inhibition by binding to the JH2 pseudokinase domain, which stabilizes the autoinhibited conformation of the TYK2 protein and prevents the activation of the JH1 catalytic domain.