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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The P light chain of cardiac myosin is phosphorylated and dephosphorylated by highly specific enzymes. These reactions take place in the beating rabbit heart and there is evidence that dephosphorylation of the light chain occurs during the inotropic response produced by adrenaline. The extent of phosphorylation of cardiac troponin I is determined by the functional state of the beating heart. During perfusion of the rabbit heart the basal phosphate content of troponin I increased from the basal level of about 1.5 moles P per mole to about 2.7 moles P per mole at the height of the inotropic response to adrenaline. The three sites of phosphorylation on troponin I are probably located in the N terminal cyanogen bromide peptide of 48 residues.
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PMID:Phosphorylation of cardiac myofibrillar proteins. 14 26

Pigeon and chicken skeletal muscle phosphorylase kinase purified to a nearly homogeneous state is able to phosphorylate both cardiac and skeletal troponin I and T. After 1-hr incubation, the enzyme transfers up to 0.35 mole of phosphorus per mole of skeletal troponin I, up to 0.5 mole of cardiac troponin I and up to 0.1 mole of cardiac and skeletal troponin T. Avian muscle phosphorylase kinase does not phosphorylate the first serine residue of cardiac and skeletal troponin T, but catalyzes the phosphate incorporation into the site(s) of troponin T located in the central or C-terminal parts of the protein molecule. The rate of troponin phosphorylation by pigeon muscle phosphorylase kinase is pH-dependent: the 6.8/8.2 ratio for troponin I is close to 0,2, whereas that with troponin T varies in the range of 0.5-0.7. Troponin phosphorylation by avian phosphorylase kinase depends on the presence of Ca2+ in the incubation mixture. In the presence of 3 mM EGTA troponin I phosphorylation is inhibited by 70-90%, whereas that of troponin T--by 50%. The experimental results indicate that the phosphorylation of troponin I and T is catalyzed either by two different active centers or by different conformations of the single center of avian phosphorylase kinase.
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PMID:[Phosphorylation of isolated components of the troponin complex of skeletal and cardiac muscle phosphorylase kinase from bird skeletal muscles]. 259 Jun 82

We have developed and validated a method that uses liquid chromatography/electrospray ionization-mass spectrometry to quantify site-specific protein phosphorylation. The method uses selected ion monitoring to determine the chromatographic peak areas of specific tryptic peptides from the protein of interest. The extent of phosphorylation is determined from the ratio of the phosphopeptide peak area to the peak area of an unmodified reference peptide that acts as internal standard, correcting for variations in protein amounts and peptide recovery in the digest preparation procedure. As a result, we refer to this protocol as the native reference peptide method. Mole of phosphate at the selected site per mole of protein is obtained from this ratio, using calibration curves of synthetic peptides to determine relative responses. Our method begins with protein separation by SDS-PAGE and is carried out on amounts of peptide produced by an in-gel digestion of single Coomassie blue-stained bands. To illustrate the utility of the method and provide validation, we used cardiac troponin I as analyte and monitored the time course of a protein kinase C betaII reaction. Those analyses appropriately demonstrate the time-dependent increase of phosphorylation at a PKC-preferred site, Ser44 in the peptide 41ISASPR45 and the concomitant consumption of the nonphosphorylated peptide. We believe that this method provides a novel tool to directly measure specific phosphorylation sites in proteins in different physiological states and expect that the method will be adaptable not only to a variety of samples types (i.e., culture cells, tissues, etc.) but to a variety of posttranslation modifications as well.
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PMID:Quantitative dynamics of site-specific protein phosphorylation determined using liquid chromatography electrospray ionization mass spectrometry. 1203 57