Data/hora: 04/06/2024 02:55:55

Provedor de dados: 	48	
País: 	Chile	
Título: 	Fast kinetics of calcium dissociation from calsequestrin	
Autores: 	BELTRÁN,MARIANELA; BARRIENTOS,GENARO; HIDALGO,CECILIA.	
Data: 	2006-01-01	
Ano: 	2006	
Palavras-chave: 	Calcium-binding proteins; Ryanodine receptors; Sarcoplasmic reticulum; Calcium release kinetics; Excitation-contraction coupling; Skeletal and cardiac muscle.	
Resumo: 	We measured the kinetics of calcium dissociation from calsequestrin in solution or forming part of isolated junctional sarcoplasmic reticulum membranes by mixing calsequestrin equilibrated with calcium with calcium-free solutions in a stopped-flow system. In parallel, we measured the kinetics of the intrinsic fluorescence changes that take place following calcium dissociation from calsequestrin. We found that at 25ºC calcium dissociation was 10-fold faster for calsequestrin attached to junctional membranes (k = 109 s-1) than in solution. These results imply that calcium dissociation from calsequestrin in vivo is not rate limiting during excitation-contraction coupling. In addition, we found that the intrinsic fluorescence decrease for calsequestrin in solution or forming part of junctional membranes was significantly slower than the rates of calcium dissociation. The kinetics of intrinsic fluorescence changes had two components for calsequestrin associated to junctional membranes and only one for calsequestrin in solution; the faster component was 8-fold faster (k = 54.1 s-1) than the slower component (k = 6.9 s-1), which had the same k value as for calsequestrin in solution. These combined results suggest that the presence of calsequestrin at high concentrations in a restricted space, such as when bound to the junctional membrane, accelerates calcium dissociation and the resulting structural changes, presumably as a result of cooperative molecular interactions.	
Tipo: 	Journal article	
Idioma: 	Inglês	
Identificador: 	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602006000300011	
Editor: 	Sociedad de Biología de Chile	
Formato: 	text/html	
Fonte: 	Biological Research  v.39 n.3 2006