Abstract
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.
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Selected References
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- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Neville D. M., Jr Molecular weight determination of protein-dodecyl sulfate complexes by gel electrophoresis in a discontinuous buffer system. J Biol Chem. 1971 Oct 25;246(20):6328–6334. [PubMed] [Google Scholar]
- Shelanski M. L., Gaskin F., Cantor C. R. Microtubule assembly in the absence of added nucleotides. Proc Natl Acad Sci U S A. 1973 Mar;70(3):765–768. doi: 10.1073/pnas.70.3.765. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sloboda R. D., Rudolph S. A., Rosenbaum J. L., Greengard P. Cyclic AMP-dependent endogenous phosphorylation of a microtubule-associated protein. Proc Natl Acad Sci U S A. 1975 Jan;72(1):177–181. doi: 10.1073/pnas.72.1.177. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Taborsky G. Phosphoproteins. Adv Protein Chem. 1974;28:1–210. doi: 10.1016/s0065-3233(08)60230-2. [DOI] [PubMed] [Google Scholar]