Potentiating effect of calmodulin and catalytic subunit of cyclic AMP‐dependent protein kinase on ATP‐dependent Ca2+‐transport by cardiac sarcolemma

[摘要]

Highly purified sarcolemmal membranes were prepared from pig heart homogenates by differential and density gradient centrifugations. The membrane fragments exhibit ATP-dependent Ca²⁺-transport and Na⁺/Ca²⁺-exchange activities. ATP-dependent Ca²⁺-transport (K Ca²⁺_0.5 = 0.3 μM; V _max = 4.6 nmol Ca²⁺•mg protein⁻¹ •min⁻¹)_is not stimulated by oxalate. Ca²⁺-uptake is also not supported by p-nitrophenylphosphate. Preincubation of sarcolemma with MgATP, calmodulin and catalytic subunit of cyclic AMP-dependent protein kinase stimulates active Ca²⁺-transport 1.8-fold. The effects of calmodulin and catalytic subunit are potentiating rather than additive. A large portion of the Ca²⁺ additionally accumulated after prephosphorylation of membranes is exchangable for Na⁺ via the Na⁺/Ca²⁺-exchange system.

[学科分类] 生物化学/生物物理

[关键词] Cardiac sarcolemma;Ca2+-pump;Protein kinase;Cyclic AMP;Calmodulin;C subunit;catalytic subunit of the cyclic adenosine 3';5'-monophosphate-dependent protein kinase;cyclic AMP;cyclic adenosine 3'5'-monophosphate;Hepes;4-(2-hydroxyethyl)-l-piperazine-ethane-sulfonic acid;EGTA;ethylene glycol bis(β-aminoethylether) N;N'-tetraacetic acid;pNPP;p-nitrophenylphosphate;TFP;trifluoperazine hydrochloride;SL;sarcolemma;SR;sarcoplasmic reticulum