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

Abstract
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.