... The PH domain of TFKs usually binds to phosphatidylino-sitol-3,4,5-trisphosphate, thereby bringing them in close proximity to other membrane-tethered signalingproteins. In SYK, the linker B region ... pro-tein kinase B (PKB)]. In AKT, a cysteine substitution of the corresponding R25 in the pleckstrin homology(PH) domain also results in loss of function [16,17],thereby demonstrating related ... locations of the missense mutation in the BTK PH domain; arginine 28 is in dark blue, encircled in red. Bottom left: SH2 domain. Right: kinasedomain. The mutated residues are indicated in yellow,...