The pseudokinase domain shows similarity to protein kinases but lacks crucial residues for catalytic activity. This subfamily is composed of the catalytically inactive kinases with similarity to yeast Scy1. It includes four mammalian proteins called SCY1-like protein 1 (SCYL1), SCYL2, SCYL3, as well as Testis-EXpressed protein 14 (TEX14). SCYL1 binds to and co-localizes with the membrane trafficking coatomer I (COPI) complex, and regulates COPI-mediated vesicle trafficking. Null mutations in the SCYL1 gene are responsible for the pathology in mdf (muscle-deficient) mice which display progressive motor neuropathy. SCYL2, also called coated vesicle-associated kinase of 104 kDa (CVAK104), is involved in the trafficking of clathrin-coated vesicles. It also binds the HIV-1 accessory protein Vpu and acts as a regulatory factor that promotes the dephosphorylation of Vpu, facilitating the restriction of HIV-1 release. SCYL3, also called ezrin-binding protein PACE-1, may be involved in regulating cell adhesion and migration. TEX14 is required for spermatogenesis and male fertility. It localizes to kinetochores (KT) during mitosis and is a target of the mitotic kinase PLK1. It regulates the maturation of the outer KT and the KT-microtubule attachment. The SCY1-like subfamily is part of a larger superfamily that includes the catalytic domains of other protein serine/threonine kinases, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
Jiyao W et al.(2023). "The conserved domain database in 2023.",