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G Bailin

Publications and source records attributed to G Bailin.

At least 37 records · Page 2Linked to original sources
PubMed1979

Phosphorylation of a bovine cardiac actin complex.

A bovine cardiac actin-tropomyosin-troponin complex was phosphorylated in the presence of [gamma-32P]ATP, Mg2+, adenosine 3',5'-monophosphate (cyclic AMP), and bovine cardiac cyclic-AMP-dependent protein kinase. Approximately 81% of the [32P]phosphate incorporated was identified as phosphoserine and phosphothreonine. Gel electrophoresis studies showed that 55% of the [32P]phosphate was associated with the inhibitory component of troponin (Tn-I) and 24% with a protein resembling the tropomyosin-binding component of troponin in the actin complex, respectively. The phosphorylation of Tn-I in the actin complex was inhibited 30% when Ca2+ was increased from 0.1 to 50 muM, but phosphorylation of other components was not affected by increasing Ca2+ concentration. Half-maximal calcium activation of the ATPase activity of reconstituted actomyosins made with the [32P]phosphorylated cardiac actin complex and cardiac myosin was shifted to Ca2+ values higher than those of actomyosins made with the nonphosphorylated actin complex.

Actins↗
PubMed1977

Phosphorylation of an actin.tropomyosin.troponin complex from human skeletal muscle.

A human skeletal actin.tropomyosin.troponin complex was phosphorylated in the presence of [gamma-32 P]ATP, Mg2+, adenosine 3':5'-monophosphate (cyclic AMP) and cyclic AMP-dependent protein kinase (protein kinase). Phosphorylation was not observed when the actin complex was incubated in the absence of protein kinase or 1 microM cyclic AMP. In the presence of 10(-7) M Ca2+ and protein kinase 0.1 mole of [32P]phosphate per 196 000 g of protein was incorporated. This was two-fold higher than the [32P]phosphate content of a rabbit skeletal actin complex but two-fold lower than that of a bovine cardiac actin complex. At high Ca2+, 5.10(-5) M, little change in the phosphorylation of a human skeletal actin complex occurred. Phosphoserine and phosphothreonine were identified in the [32P]phosphorylated actin complex. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that 60% of the label was associated with the tropomyosin binding component of troponin. The inhibitory component of troponin contained 16% of the bound [32P]phosphate. Increasing the Ca2+ concentration did not significantly decrease the [32P]phosphate content of the phosphorylated proteins in the actin complex. No change in the distribution of phosphoserine or phosphothreonine was observed. Half maximal calcium activation of the ATPase activity of reconstitute human skeletal actomyosin made with the [32P] phosphorylated human skeletal actin complex was the same as a reconstituted actomyosin made with an actin complex incubated in the absence of protein kinase at low or high Ca2+.

Actins↗
PubMed1977

Cooperative interactions between the contractile proteins of cardiac and skeletal muscle.

The calcium activation of the ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity of cardiac actomyosin reconstituted from bovine cardiac myosin and a complex of actin-tropomyosin-troponin extracted from bovine cardiac muscle at 37 degrees C was studied and compared with similar proteins from rabbit fast skeletal muscle. The proteins of the actin complex were identified by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Half-maximal activation of the cardiac actomyosin was seen at a calcium concentration of 1.2 +/- 0.002 (S.E. of mean) muM. A hybridized reconstituted actomyosin made with cardiac myosin and the actin-tropomyosin-troponin complex extracted from rabbit skeletal muscle was also activated by calcium but the half-maximal value was shifted to 0.65 +/- 0.02 (S.E. of mean) muM Ca2+. Homologous rabbit skeletal actomyosin showed half-maximal activation at 0.90 +/- 0.01 (S.E. of mean) muM Ca2+ and the value for a hybridized actomyosin made with rabbit skeletal myosin and the actin-complex from cardiac muscle was found at 1.4 +/- 0.03 (S.E. of mean) muM Ca2+ concentration. Kinetic analysis of the Ca2+ activated ATPase activity of reconstituted bovine cardiac actomyosin indicated some degree of cooperativity with respect to calcium. Double reciprocal plots of reconstituted actomyosins made with bovine cardiac actin complex were curvilinear and significantly different than those of reconstituted actomyosins made with the rabbit fast skeletal actin complex. The Ca2+-dependent cooperativity was of a mixed type as determined from Hill plots for homologous reconstituted bovine cardiac and rabbit fast skeletal actomyosin. The results show that cooperative interactions in reconstituted actomyosins were greater when the actin-tropomyosin-troponin complex was derived from cardiac than skeletal muscle.

Actins↗
PubMed1976

Myosin and actomyosin from human skeletal muscle.

Human skeletal natural actomyosin contained actin, tropomyosin, troponin and myosin components as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. Purified human myosin contained at least three light chains having molecular weights (+/-2000) of 25 000, 18 000 and 15 000. Inhibitory and calcium binding components of troponin were identified in an actin-tropomyosin-troponin complex extracted from acetone-dried muscle powder at 37 degrees C. Activation of the Mg-ATPase activity of Ca2+-sensitive human natural or reconstituted actomyosin was half maximal at approximately 3.4 muM Ca2+ concentration (CaEGTA binding constant equals 4.4 - 10(5) at pH 6.8). Subfragment 1, isolated from the human heavy meromyosin by digestion with papain, appeared as a single peak after DEAE-cellulose chromatography. In the pH 6-9 range, the Ca2+-ATPase activity of the subfragment 1 was 1.8- and 4-fold higher that the original heavy meromyosin and myosin, respectively. The ATPase activities of human myosin and its fragments were 6-10 fold lower than those of corresponding proteins from rabbit fast skeletal muscle. Human myosin lost approximately 60% of the Ca2+-ATPase activity at pH 9 without a concomitant change in the number of distribution of its light chains. These findings indicate that human skeletal muscle myosin resembles other slow and fast mammalian muscles. Regulation of human skeletal actomyosin by Ca2+ is similar to that of rabbit fast or slow muscle.

Actins↗
PubMed1975

Dinitrophenylation of rabbit skeletal actomyosin.

Dinitrophenylated reconstituted or natural actomyosin effected changes in the Ca2+ sensitivity which were dependent upon the ionic strength of the reaction medium. Dinitrophenylation of reconstituted actomyosin in 0.6 M KCl led to the incorporation of 2-6 mol of the reagent per 5-10(5) g of protein and it possessed considerable Ca2+ sensitivity. Dinitrophenylated natural actomyosin under the same conditions lost most of its Ca2+ sensitivity when 1.3-5.4 mol of the dinitrophenyl group were bound. The myosin from these modified actomyosins did not lose Ca2+ sensitivity and the myosin was labeled only with 0.4-1.7 mol of the dinitrophenyl group. Dinitrophenylation of both kinds of actomyosin in 0.06 M KCl abolished the Ca2+ sensitivity; the myosin from the modified actomyosins also lost Ca2+ sensitivity. Myosin alone was more susceptible to a loss of Ca2+ sensitivity than myosin in actomyosin. Actin protected the ability of myosin to sense Ca2+ regulated actin in modified actomyosin at 0.6 M KCl but not at 0.06 M KCl. Actomyosin dinitrophenylated in the presence of ATP lost Ca2+ sensitivity. However, the myosin from this actomyosin possessed Ca2+ sensitivity. Thiolysis of the dinitrophenylated actomyosin by 2-mercaptoethanol at low ionic strength did not restore the Ca2+ sensitivity of this actomyosin or its myosin although there was a significant loss of the dinitrophenyl group.

Actomyosin↗