海綿由来の新規SH基修飾薬Xestoquinoneによる筋収縮機構の解析 [in Japanese] Analysis of the mechanism of muscle contraction by using xestoquinone, a novel SH reagent isolated from a sea sponge [in Japanese]
Access this Article
Search this Article
Xestoquinone isolated from an Okinawan sea sponge <I>Xestospongia sapra</I> inhibited both Ca<SUP>2+</SUP>- and K<SUP>+</SUP> (EDTA)-ATPase but not Mg<SUP>2+</SUP>-ATPase of skeletal muscle myosin. The inhibition was abolished in the presence of dithiothreitol. However, xestoquinone unlike N-ethylmaleimide, a well-known sulfhydryl (SH)<SUP>1</SUP> reagent markedly activated actomyosin ATPase. Modification of 2 moles of SH groups per myosin by xestoquinone caused a marked increase in the actomyosin ATPase activity. Kinetical analysis of stimulatory effects of xestoquinone indicates decrease in the actin concentrations which gives half of the maximum velocity (V<SUB>max</SUB>) of actomyosin ATPase reaction without affecting the V<SUB>max</SUB>, suggesting the increase in the affinity of myosin for actin. N-ethylmaleimide can modify both the SH<SUB>1</SUB> and SH<SUB>2</SUB> groups still after modification of 2 mole SH groups by xestoquinone. Xestoquinone modified myosin SH groups to cause a change in the fluorescence intensity of intrinsic tryptophan residues and circular dichroism. These results suggest that xestoquinone modifies the specific SH groups in myosin distinct from SH<SUB>1</SUB> and SH<SUB>2</SUB> resulting in activation of actomyosin ATPase. It is also suggested that xestoquinone strengthens the interaction between actin and myosin through conformational change in myosin molecule.
- Folia Pharmacologica Japonica
Folia Pharmacologica Japonica 106, 92-96, 1995-09-01
The Japanese Pharmacological Society