Characterization of additional casein kinase I sites in the C-terminal "tail" region of chicken and rat neurofilament-M.
In previous studies we have identified Ser502, Ser528, and Ser534 as target sites in chicken neurofilament middle molecular mass protein (NF-M) for casein kinase I (CKI) in vitro and have shown that these sites are also phosphorylated in vivo. We now make use of a combination of molecular biological and protein chemical techniques to show that two additional in vivo phosphorylation sites in chicken NF-M, Ser464 and Ser471, can also be phosphorylated by CKI in vitro. These two sites are conserved in higher vertebrate NF-M molecules, and recombinant protein constructs containing the homologous rat NF-M peptides can be phosphorylated by CKI in vitro, suggesting that phosphorylation of these sites is conserved at least in higher vertebrates. The two new sites are adjacent to a conserved peptide sequence (VEEIIEET-V) found once in higher vertebrate NF-M molecules and twice in lamprey NF-180. Variants of this sequence are also found in neurofilament low and high molecular mass proteins (NF-L and NF-H) and alpha-internexin, and in mammalian NF-L are known to be associated with in vivo phosphorylation sites. We speculate that CKI phosphorylation in general, and these sites in particular, may be important in neurofilament function.
Shaw
G
G
Department of Neuroscience and Brain Institute, University of Florida College of Medicine, Gainesville, U.S.A.
Miller
R
R
Wang
D S
DS
Tang
D
D
Hollander
B A
BA
Bennett
G S
GS
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D047388:Casein Kinases; D002645:Chickens / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D016900:Neurofilament Proteins / Q000235:genetics* / Q000378:metabolism*; D010449:Peptide Mapping; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats / Q000235:genetics / Q000378:metabolism*
D016900:Neurofilament Proteins; C061195:neurofilament protein M; D011494:Protein Kinases; D047388:Casein Kinases