SSTK-interacting protein, TSSK6-activating co-chaperone protein
SSTK-IP, SSTK-interacting protein or TSSK6-activating co-chaperone, is a family of proteins found in eukaryotes. SSTK-IP directly binds to HSP70, is found associated with HSP70 and HSP90 in cells, and facilitates HSP90-dependent enzymatic activation of SSTK. SSTK is a small serine/threonine kinase expressed post-meiotically and essential for male fertility along with two other serine threonine kinases. SSTK is one of the smallest protein kinases, consisting only of N- and C-lobes of a kinase catalytic domain, and forms stable associations with heat shock protein (HSP) 70 and 90. SSTK-IP, its interacting protein, thus represents the first germ cell-specific co-chaperone and protein kinase that requires the HSP90 machinery for catalytic activation.