General Characteristics of the Superprecipitation Reaction of Rat Crude Uterine Myosin B: Effects of L-Methionine and/or Transmethylation Blockers on the Reaction

Abstract

The characteristics of superprecipitation of uterine myosin B from 17β-estradiol-3-benzoate-treated rats and the effects of L-methionine and/or 3-deazaadenosine (3-DAA) plus homocysteine thiolactone (HCTL) on the reaction were investigated. The slope and plateau phases of the superprecipitation were dependent on ATP, calcium and magnesium. The calmodulin antagonists, trifluoperazine and N-(6-aminohexyl)-5-chloro-1 -naphthalene sulfonamide, inhibited the slope and plateau phases, but not the basal superprecipitation. SDS-polyacrylamide gel electrophoresis of the precipitate obtained in complete medium showed the presence of actin and myosin. Addition of 3 mM L-methionine had little affect on either the slope or plateau phases of the basal- or calcium-dependent superprecipitation, while 500 μM 3-DAA plus 1 mM HCTL caused only 9 to 20% decrease in the calcium-dependent superprecipitation in the presence of 0.1 mM or 1 mM ATP. These findings suggest that the calcium-dependent superprecipitation of rat uterine myosin B reflected the contractile response of uterine muscle, and that L-methionine and/or 3-DAA plus HCTL did not affect the calcium-dependent superprecipitation of uterine myosin B.