Tyrosine Tubulin Kinases in Particulate Fractions from Rat Cerebral Cortex
HiroshimaJMedSci_36_395.pdf 5.54 MB
Tyrosine protein kinase
Tyrosine tubulin kinase activity in the particulate fractions from rat cerebral cortex was quantitatively solubilized and separated into two active peaks (kinase I and kinase II) by Sephacryl S-300 gel-filtration in the presence of 0.2% Nonidet P-40. Kinases I and II were each resolved into 5 active peaks (I-1→5 and II-1→5) by casein-Sepharose column chromatography. The molecular weights of these kinases were estimated from the s20,w values to be 59,000-65,000. Tyrosine-glutamate (1:4) copolymers were also substrates for the enzymes. About 60% of the copolymers kinase activity in I-3, I-4, II-3 and II-4 were immunoprecipitable with saturating amount of monoclonal antibody (MAb 327) that recognizes pp60^c-src. The Km values of II-3 and II-4 for tubulin were nearly 10 times higher than those of I-3 and I-4. However, the Km values of the four kinases for the copolymers were not so significantly different. In comparison with the II-3 and II-4 kinase fractions, I-3 and I-4 fractions showed 2 and 10 times higher activity ratios with tubulin and the IgG heavy chain of MAb 327 relative to the copolymers kinase activity. Incubation of the immunocomplexes with ATP at 0°C for 10 min resulted in the autophosphorylation of a 60kDa protein in I-3 and I-4 but not in II-3 and II-4.
Hiroshima Journal of Medical Sciences
Hiroshima University Medical Press