We have observed the phosphorylation of neurofilament protein from squid axoplasm. Phosphorylation is demonstrated by 32P labeling of protein during incubation of axoplasm with [gamma-32P]ATP. When the labeled proteins are separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), two bands, at 2.0 x 10(5) daltons and greater than 4 x 10(5) daltons, contain the bulk of the 32P. The 2.0 x 10(5)-dalton phosphorylated polypeptide comigrates on SDS-PAGE with one of the subunits of squid neurofilament protein. Both major phosphorylated polypeptides co-fractionate with neurofilaments in discontinuous sucrose gradient centrifugation and on gel filtration chromatography on Sepharose 4B. The protein-phosphate bond behaves like a phospho-ester, and labeled phospho-serine is identified in an acid hydrolysate of the protein. The generality of this phenomenon in various species and its possible physiological significance are discussed.
Article| August 01 1978
Neurofilament protein is phosphorylated in the squid giant axon.
H C Pant
R J Lasek
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1978) 78 (2): R23.
H C Pant, G Shecket, H Gainer, R J Lasek; Neurofilament protein is phosphorylated in the squid giant axon.. J Cell Biol 1 August 1978; 78 (2): R23–7. doi: https://doi.org/10.1083/jcb.78.2.R23
Download citation file: