Mycalolide-B, a novel and specific inhibitor of actomyosin ATPase isolated from marine sponge.
A toxin isolated from marine sponge, mycalolide-B, inhibited smooth muscle contractions without changing cytosolic Ca2+ levels. It also inhibited Ca(2+)-induced contraction in permeabilized smooth muscles. In native actomyosin prepared from chicken gizzard, mycalolide-B inhibited superprecipitation and Mg(2+)-ATPase activity stimulated by Ca2+ without changing myosin light chain phosphorylation. In the permeabilized muscle and native actomyosin preparation thiophosphorylated with ATP gamma S, mycalolide-B inhibited ATP-induced contraction and Mg(2+)-ATPase activity, respectively, in the absence of Ca2+. Mycalolide-B also inhibited Mg(2+)-ATPase activity of skeletal muscle native actomyosin. Mycalolide-B had no effect on calmodulin-stimulated (Ca(2+)-Mg2+)-ATPase activity of erythrocyte membranes. These results suggest that mycalolide-B selectively inhibits actin-myosin interaction.
Hori
M
M
Department of Veterinary Pharmacology, Faculty of Agriculture, University of Tokyo, Japan.
Saito
S
S
Shin
Y Z
YZ
Ozaki
H
H
Fusetani
N
N
Karaki
H
H
D000199:Actins / Q000187:drug effects; D000818:Animals; D002645:Chickens; D066298:In Vitro Techniques; D008297:Male; D008387:Marine Toxins; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009218:Myosins / Q000037:antagonists & inhibitors* / Q000187:drug effects; D010080:Oxazoles / Q000494:pharmacology*; D011161:Porifera; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar
D000199:Actins; D008387:Marine Toxins; D010080:Oxazoles; C080978:mycalolide B; D009218:Myosins