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首页> 外文期刊>Biochemistry >Comparison of the kinetic effects of phospholamban phosphorylation and anti-phospholamban monoclonal antibody on the calcium pump in purified cardiac sarcoplasmic reticulum membranes
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Comparison of the kinetic effects of phospholamban phosphorylation and anti-phospholamban monoclonal antibody on the calcium pump in purified cardiac sarcoplasmic reticulum membranes

机译：纯化的心脏肌浆网膜中磷酸lamban磷酸化和抗phospholamban单克隆抗体对钙泵的动力学作用比较

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摘要

Protein kinase A- (PKA-) catalyzed phosphorylation of phospholamban (PLN), the protein regulator of the cardiac Ca pump, mediates abbreviation of systole in response to beta-adrenergic agonists. Investigators previously, however, have been unsuccessful in demonstrating an effect of PLN phosphorylation or anti-PLN monoclonal antibody (mAb), which is considered to mimic phosphorylation's well-known effect on Km(Ca), on microsomal Ca uptake at the (high) Ca2+ concentrations found intracellularly at peak systole. We therefore compared the effects of the catalytic subunit of PKA and anti-PLN mAb on the kinetics of Ca uptake in sucrose gradient-purified cardiac microsomes. Both treatments produced a 33-44% increase in Vmax(Ca) at 25 and 37 degrees C, and an 11-31% decrease in Km(Ca) with comparable changes in Ca2+-ATPase activity. An acceleration of E2P decomposition upon PLN phosphorylation may contribute to the increased Vmax(Ca) of Ca uptake at 25 degrees C but not at 37 degrees C, based on measurement of the kinetics of E2P decomposition and steady-state E2P formation from Pi at different temperatures. Our data document almost identical increases in Vmax(Ca) of microsomal Ca uptake with PLN phosphorylation or addition of anti-PLN mAb and hence provide insight into the kinetic mechanism of PLN's regulation of the cardiac sarcoplasmic reticulum Ca pump protein.
机译：蛋白激酶A-（PKA-）催化磷酸Calamban（PLN）（心脏Ca泵的蛋白调节剂）的磷酸化介导收缩期的缩写，以响应β-肾上腺素能激动剂。但是，以前的研究人员未能证明PLN磷酸化或抗PLN单克隆抗体（mAb）的作用，该作用被认为模仿了磷酸化对Km（Ca）的众所周知的作用，该作用对（高） Ca2 +浓度在收缩期高峰时在细胞内发现。因此，我们比较了蔗糖梯度纯化心脏微粒体中PKA和抗PLN mAb催化亚基对钙吸收动力学的影响。两种处理在25和37摄氏度下均使Vmax（Ca）升高33-44％，Km（Ca）降低11-31％，且Ca2 + -ATPase活性变化相当。根据E2P分解的动力学和从Pi在不同温度下形成稳态E2P的测量结果，PLN磷酸化后E2P分解的加速可能有助于增加Ca的吸收（在25摄氏度而不是在37摄氏度时）的Vmax（Ca）。温度。我们的数据记录了PLN磷酸化或添加抗PLN mAb引起的微粒体Ca吸收的Vmax（Ca）几乎相同的增加，因此可提供PLN调节心肌肌浆网Ca泵蛋白的动力学机制的见解。

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