Tyrosine kinase 2 JH2 pseudokinase domain (TYK2 JH2)

The tyrosine kinase 2 JH2 pseudokinase domain (TYK2 JH2) is a regulatory domain of the Janus kinase TYK2, part of a subfamily of non-receptor tyrosine kinases essential for cytokine receptor signaling in immune cells[1][2][4][5][6]. The JH2 domain, called a pseudokinase because it lacks canonical catalytic activity, plays a critical allosteric role: it maintains the adjacent JH1 tyrosine kinase domain in an autoinhibited conformation until receptor dimerization and ligand binding trigger activation[1][2][3]. TYK2 JH2 can bind ATP, which stabilizes its structure but does not confer phosphotransfer activity[4]. Targeting TYK2 JH2 with small molecules stabilizes its autoinhibited state, selectively blocking cytokine signaling downstream of IL-12, IL-23, and interferon receptors without broadly affecting the Janus kinase (JAK) family, providing a potentially safer therapeutic strategy in autoimmunity and inflammation[1][5]. Drugs such as deucravacitinib act allosterically via this domain, representing a novel class of selective kinase inhibitors. Safety concerns relate to immunosuppression, but JH2-selective compounds are generally less prone to adverse effects seen with pan-JAK inhibition[1].

Other names

TYK2 pseudokinase domainJanus kinase 2 JH2 pseudokinase domain (less common, potentially confusing with JAK2, use with caution)TYK2 JH2

Allosteric inhibition of TYK2, blocking receptor-mediated activation of the kinase domain and downstream cytokine signaling (e.g., IL-12, IL-23, IFN)[1][4][5] Stabilization of the pseudokinase domain to maintain an autoinhibited state[1][5]