RESUMO
It is shown that endogenic phosphorylation of sarcoplasmatic reticulum membranes in white skeletal muscles of rabbit stimulates Mg2+, Ca2+-ATPase activity and Ca2+ accumulation. When the level of endogenic phosphorylation is high, exogenic cAMP and protein kinase do not affect Mg2+, Ca2+-ATPase activity, when the level is low, they produce a 1.5-2-fold increase in the activity. The inhibitor of cAMP-dependent protein kinase practically completely eliminates the effect of endogenic phosphorylation on Ca2+ accumulation and Mg2+, Ca2+-ATPase activity. Under endogenic phosphorylation the Ca2+ binding constant becomes 1.8 times as low in sites of high affinity for this ion, and 4 times as low--in sites of low affinity.
Assuntos
ATPases Transportadoras de Cálcio/metabolismo , Cálcio/metabolismo , AMP Cíclico/fisiologia , Proteínas Musculares/metabolismo , Retículo Sarcoplasmático/metabolismo , Adenilil Ciclases/metabolismo , Animais , Transporte Biológico , ATPase de Ca(2+) e Mg(2+) , Técnicas In Vitro , Fosforilação , Proteínas Quinases/metabolismo , Coelhos , Retículo Sarcoplasmático/enzimologiaAssuntos
Cálcio/metabolismo , Sarcolema/metabolismo , Adsorção , Animais , Sítios de Ligação , Técnicas In Vitro , CoelhosRESUMO
It is established that Ca2+ binding with rabbit skeletal muscles plasmatic membrane depends on this cation concentration in the incubating medium. pH, temperature, incubation period and presence of Mg ions in the medium affect the Ca2+-binding ability of sarcolemma. The entropic changes observed in sarcolemma Ca2+ binding are due to conformation reconstructions of the membrane components.