Macromolecular characterization of muscle membranes. Endogenous membrane kinase and phosphorylated protein substrate from normal and denervated muscle.

摘要: Light density membranes derived from the "microsomal" fraction of rat skeletal muscle contained an endogenous protein kinase which catalyzed phosphorylation membrane substrate. No other any significant activity. The optimal specific activity enzyme in these was 350 pmol/mg/min. required magnesium, stimulated by micromolar concentrations calcium, had a pH optimum between 7.0 and 7.5, demonstrated K-m for ATP 2.6 times 10 minus 5 M. markedly heat labile linear Arrhenius plot with apparent energy activation 12,100 cal/mol. There no stimulation cyclic nucleotides; neither monovalent cations nor various neurotransmitters exerted effect. It is presently unclear where exhibiting are localized within fiber. Enzyme markers suggest that not sarcolemma or sarcoplasmic reticulum but may originate transverse tubules. largely confined to polypeptide molecular weight 28,000. Phosphorylation could also be detected lower substrate as well two polypeptides weights 95,000 56,000. M-r-28,000 isolated preparative gel electrophoresis sodium dodecyl sulfate. High voltage partial acid hydrolysate phosphorylated identified phosphate bond phosphoserine. amino composition strongly acidic basic. high content glycine, glutamic acid, serine, lysine. Hydrophobic residues constituted only 45% total composition. Following denervation days, there decrease amount extent phosphorylation.