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Effects of canatoxin on the Ca(2+)-ATPase of sarcoplasmic reticulum membranes
E W Alves1, A T Ferreira, C T Ferreira
1Departamento de Bioquimica Medica, Instituto de Ciencias Biomedicas, Universidade Federal do Rio de Janeiro, Brazil.
Abstract:
Canatoxin, a toxic protein isolated from the seeds of Canavalia ensiformis, was studied for its effects on the sarcoplasmic reticulum vesicles obtained from rabbit skeletal muscle. Canatoxin inhibited Ca2+ accumulation catalysed by the Ca(2+)-ATPase, without affecting the hydrolytic activity of this enzyme or membrane permeability to Ca2+. The effects of canatoxin were dose dependent, but not time dependent. It is concluded that canatoxin interacts with the Ca2+ pump and uncouples Ca2+ uptake from Ca(2+)-dependent ATP hydrolysis.