Reaction mechanism of Mn2+-ATPase of acto-H-meromyosin in 0.1 M KCl at 5 degrees C: evidence for the Lymn-Taylor mechanism.
The rate constants of a series of elementary steps in the H-meromyosin (HMM) Mn2+-ATPase [EC 3.6.1.3] and acto-HMM Mn2+-ATPase reactions were determined in 0.1 M KCl at 5 degrees C. We found that the rate-limiting step in the HMM Mn2+-ATPase reaction was the liberation of ADP from HMM.ADP, of which the rate constant was estimated to be 0.17 s-1. All the results obtained with the acto-HMM Mn2+-ATPase reaction could be quantitatively explained by a modified Lymn-Taylor mechanism (see Fig. 15). The second-order rate constant for the dissociation of acto-HMM induced by ATP was 3.0 X 10(5) M-1.s-1, and that for the Pi burst in the acto-HMM ATPase reaction was 1.7 X 10(5) M-1.s-1. The second-order rate constant for the binding of HMM.ADP with F-actin was 0.25 s-1.mg-1.ml, and the rate-limiting step in the acto-HMM Mn2+-ATPase reaction was the conversion of HMMPADP into HMM.ADP plus Pi, when the F-actin concentration was high.
D000199:Actins / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology*; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D011189:Potassium Chloride; D011817:Rabbits; D013696:Temperature
D000199:Actins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D010710:Phosphates; D008345:Manganese; D000244:Adenosine Diphosphate; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D009218:Myosins