title: Proline-directed protein kinase (p34cdc2/p58cyclin A) phosphorylates bovine neurofilaments.
abstract: Proline-directed protein kinase (PDPK), a complex of p34cdc2 and p58cyclin A, phosphorylates bovine neurofilaments (NFs) in vitro. Incubation of intact filaments with PDPK led to strong labeling of the heavy (NF-H) and middle (NF-M) molecular weight NF proteins and weaker labeling of the low molecular weight protein (NF-L). All three proteins were phosphorylated in solution, with the best substrate being NF-H. Proteins that had been dephosphorylated by enzymatic treatment were better substrates than native proteins--as many as 6 mol of phosphate were incorporated per mole of NF-H. Partial proteolytic cleavage experiments combined with two-dimensional peptide mapping indicated that NF-H and NF-M were phosphorylated predominantly in the tail domains, with some phosphate also appearing in the heads. Soluble NF-L is phosphorylated on the head domain peptide L-3, whereas NF-L within intact filaments is phosphorylated only on the tail domain peptide L-1. Phosphorylation does not lead to filament disassembly. A possible role for PDPK in NF phosphorylation in vivo is discussed.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Long Beach 90840.
authors.forename: R J
authors.initials: RJ
authors.lastname: Guan
authors.forename: F L
authors.initials: FL
authors.lastname: Hall
authors.forename: J A
authors.initials: JA
authors.lastname: Cohlberg
mesh_terms: D000818:Animals; D001345:Autoradiography; D002417:Cattle; D007382:Intermediate Filaments / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D016900:Neurofilament Proteins / Q000378:metabolism; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D038461:Proline-Directed Protein Kinases; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D016900:Neurofilament Proteins; D010748:Phosphopeptides; C044882:neurofilament protein L; C051774:neurofilament protein H; C061195:neurofilament protein M; D011494:Protein Kinases; D038461:Proline-Directed Protein Kinases