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首页> 外文期刊>The Open Biochemistry Journal >Properties of the SR Ca-ATPase in an Open Microsomal Membrane Preparation
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Properties of the SR Ca-ATPase in an Open Microsomal Membrane Preparation

机译:开式微粒体膜制备中SR Ca-ATPase的性质

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摘要

SR vesicles isolated from rabbit muscle were treated by a SDS incubation and subsequent dialysis to obtain open membrane fragments that allow a direct access to the luminal membrane surface and especially to the ion-binding sites in the P-E2 conformation of the Ca-ATPase. The open membrane fragments showed about 80% of the enzyme activity in the untreated membranes. Pump function was investigated by using electrochromic styryl dyes. The kinetic properties of cytoplasmic ion binding showed no significant differences between the Ca-ATPases in SR vesicles and in membrane fragments. From pH-dependent Ca2+ binding it could be deduced that due to the SDS treatment the density of negatively charged lipid was increased by one elementary charge per 12 lipid molecules. Major differences between Ca-ATPase from SR vesicles and membrane fragments were the respective fluorescence amplitudes. This effect is, however, produced by dye-lipid interaction and not by pump function. It was demonstrated that time-resolved kinetics may be study by the use of caged compounds such as caged ATP or caged calcium also in the case of the membrane fragments.
机译:通过SDS孵育和随后的透析处理从兔肌肉分离的SR囊泡,获得开放的膜碎片,该膜碎片可直接进入腔膜表面,尤其是Ca-ATPase的P-E2构象中的离子结合位点。开放的膜碎片在未处理的膜中显示出约80%的酶活性。通过使用电致变色苯乙烯基染料研究泵功能。胞质离子结合的动力学特性表明SR囊泡和膜碎片中的Ca-ATPase之间没有显着差异。从pH依赖的Ca2 +结合可以推断出,由于SDS处理,带负电荷的脂质的密度每12个脂质分子增加一个元素电荷。 SR囊泡中Ca-ATPase和膜碎片之间的主要区别是各自的荧光幅度。但是,这种效果是由染料-脂质相互作用而不是由泵功能产生的。已经证明,在膜碎片的情况下,也可以通过使用笼状化合物如笼状ATP或笼状钙来研究时间分辨动力学。

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