| Sak serine threonine kinase acts as an effector of Tec tyrosine kinase . ^^^ One of such Tec binding proteins turned out to be Sak . ^^^ In human kidney 293 cells , Sak became tyrosine phosphorylated by Tec , and the serine threonine kinase activity of Sak was detected only under the presence of Tec , suggesting Sak to be an effector molecule of Tec . ^^^ In addition , Tec activity efficiently protects Sak from the `` PEST ' ' sequence dependent proteolysis . ^^^ |