Serine/Threonine Kinase 17B (STK17B)

The full-length STK17B cDNA clone encodes a deduced 372-amino acid protein with a molecular mass of 42.34 kD. The putative kinase domain is located at the N terminus and contains all 11 subdomains conserved among ser/thr kinases. STK17A and STK17B share 59.7% amino acid identity. Northern blot analysis revealed that STK17B is expressed in various tissues, such as heart, placenta, liver, and pancreas, as different sized transcripts, presumably due to differences in the 3-prime untranslated region. An in vitro assay demonstrated that STK17B is capable of autophosphorylation and of phosphorylating myosin light chain as an exogenous substrate, but with lower kinase activity than STK17A. Unlike STK17A, an STK17B mutant lacking the noncatalytic C terminus had higher kinase activity than the full-length STK17B.