title: Reversible dissociation of dog cardiac myosin regulatory light chain 2 and its influence on ATP hydrolysis.
abstract: The regulatory light chains of dog heart myosin were removed by digestion with myopathic hamster neutral protease. The heavy chains were also cleaved to an extent of 15%, but a homogeneous, rod-free LC2-deficient myosin was obtained by ion-exchange chromatography. A similar approach was used to prepare LC2-deficient heavy meromyosin. Neither Ca2+- nor K+-EDTA-activated ATPases were affected by LC2 removal. The Lineweaver-Burk plots for actin-activated ATPase in 25 mM KCl were biphasic giving a Vmax of 1.54 s-1 for control and LC2-recombined myosins and 1.08 s-1 for LC2-deficient myosin at low actin concentrations. At high actin concentrations, the Vmax for control and recombined myosins was 2.33 s-1 and 1.39 s-1 for LC2-deficient myosin. Increasing the KCl concentration in the reaction mixtures resulted in more linear plots without suppressing the 35-45% decrease in Vmax that accompanied LC2 removal. The results from assays with control and LC2-deficient heavy meromyosin performed in the absence of KCl, paralleled those obtained with myosin. The latter was also assayed in the presence of equimolar concentrations of C-protein in 50 mM KCl: C-protein induced a significant increase in the actin-activated ATPase of both control and LC2-recombined myosins, with no effect on LC2-deficient myosin. The Vmax for actin-activation in the presence of C-protein was 2.38 s-1, 0.83 s-1, and 1.71 s-1 for control, LC2-deficient, and recombined myosins, respectively. The enhancement of actin-activation in both the control and LC2-recombined myosins represents a possible role for C-protein in a LC2-mediated potentiation of actomyosin ATPase.
authors.forename: S S
authors.initials: SS
authors.lastname: Margossian
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins; D006224:Cricetinae; D004285:Dogs; D004492:Edetic Acid / Q000494:pharmacology; D010450:Endopeptidases / Q000494:pharmacology; D006868:Hydrolysis; D007700:Kinetics; D009124:Muscle Proteins / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology*; D015879:Myosin Subfragments; D009218:Myosins / Q000032:analysis*; D015260:Neprilysin; D000099163:Myosin Binding Protein C
chemical_list: D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D002352:Carrier Proteins; D004492:Edetic Acid; D010450:Endopeptidases; D009124:Muscle Proteins; D015879:Myosin Subfragments; D009218:Myosins; D015260:Neprilysin; D000099163:Myosin Binding Protein C