Clathrin β-light chain of rat liver coated vesicles is phosphorylated in vitro and in vivo

Clathrin β-light chain of rat liver coated vesicles is phosphorylated in vitro in the presence of poly(L-lysine) by an endogenous protein kinase which appears to be similar to casein kinase II. Clathrin β-light chain is also phosphorylated in vivo. After injection of [ 32P]phosphate into rats and preparation of purified coated vesicles in the presence of phosphatase inhibitors, electrophoretic analysis showed the presence of several labeled polypeptides including clathrin β-light chain. A polypeptide of 50 kDa, which may correspond to the major polypeptide phosphorylated in vitro of coated vesicles, is also labeled in vivo.