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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Crosslinking the active site of sarcoplasmic reticulum Ca(2+)-ATPase completely blocks Ca2+ release to the vesicle lumen.
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Crosslinking the active site of sarcoplasmic reticulum Ca(2+)-ATPase completely blocks Ca2+ release to the vesicle lumen.

机译：交联的肌浆网C​​a（2 +）-ATPase的活性位点完全阻止Ca2 +释放到囊泡腔。

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摘要

Intramolecular crosslinking of the active site of the sarcoplasmic reticulum Ca(2+)-ATPase with glutaraldehyde results in substantial inhibition of ATPase activity and stabilization of the ADP-sensitive E1 approximately P(2Ca) intermediate (E, enzyme) with occluded Ca2+ [Ross, D. C., Davidson, G. A. & McIntosh, D. B. (1991) J. Biol. Chem. 266, 4613-4621]. We show here, using conditions of low passive vesicle permeability and absence of ADP, that Ca2+ "deoccludes" more rapidly than it leaks out of the vesicle lumen. Deocclusion is paralleled by dephosphorylation. Therefore, turnover of crosslinked E1 approximately P(Ca) (approximately 5 nmol/min per mg of protein at 25 degrees C) involves Ca2+ release to the vesicle exterior and concomitant phosphoenzyme hydrolysis. Ca2+ release to the lumen, the normal pathway, is apparently blocked completely. In the presence of ADP, Ca2+ is also released to the vesicle exterior, and this release is coupled to the synthesis of ATP. The results suggest that a tertiary structural change at the active site follows phosphorylation and is an absolute requirement for Ca2+ release from the native enzyme to the vesicle lumen.
机译：肌浆网Ca（2 +）-ATPase的活性位点与戊二醛的分子内交联导致ATPase活性的实质性抑制和对ADP敏感E1大约P（2Ca）中间物（E，酶）的封闭Ca2 +的稳定作用[罗斯，DC，Davidson，GA和McIntosh，DB（1991）J.Biol.Chem.Soc。，2004，9，1937。化学266，4613-4621]。我们在这里显示，在低被动性囊泡通透性和缺乏ADP的条件下，Ca2 +比从囊泡腔中泄漏的速度更快。去阻塞与去磷酸化平行。因此，交联的E1的周转量大约为P（Ca）（在25摄氏度下每mg蛋白质大约5 nmol / min）涉及Ca2 +释放到囊泡外部和伴随的磷酸酶水解。 Ca2 +释放至管腔（正常途径）显然被完全阻断。在存在ADP的情况下，Ca 2+也释放到囊泡外部，并且该释放与ATP的合成偶联。结果表明，在活性位点的三级结构变化是磷酸化之后的，这是从天然酶向囊泡内腔释放Ca2 +的绝对要求。

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