DOMAIN- AND SITE-SPECIFIC PHOSPHORYLATION OF BOVINE NF-L BY RHO-ASSOCIATED KINASE

Rho-associated kinase (Rho-kinase), the putative target of the small G TP-binding protein Rho, phosphorylated neurofilament protein (NF-L) in vitro with approximately 1 mole phosphate per mole NF-L. Phosphorylat ed NF-L no longer formed the 10 nm filaments, and NF-L filaments were phosphorylated with a result of nearly complete disassembly. NF-L phos phorylated by Rho-kinase was digested with trypsin, and digested fragm ents were assigned by MALDI/TOF. Unique phosphorylation sites were fou nd at Ser-26 and Ser-57 in the head domain of NF-L. These results indi cate that domain-and site-specific phosphorylation by Rho-kinase may r egulate the assembly disassembly of NF-L filaments. (C) 1998 Academic Press.