Dux L, Martonosi A
Eur J Biochem. 1984 May 15;141(1):43-9. doi: 10.1111/j.1432-1033.1984.tb08154.x.
Crystalline arrays of Ca2+ transport ATPase develop in sarcoplasmic reticulum membranes after treatment with Na3VO4 in a calcium-free medium [ Dux , L. and Martonosi , A. (1983) J. Biol. Chem. 258, 2599-2603]. The proportion of vesicles containing Ca2+-ATPase crystals in microsome preparations isolated from rat muscle of different fiber types (semimembranosus, levator ani, extensor digitorum longus, diaphragm, soleus, and heart) correlates well with the Ca2+-ATPase content and Ca2+-modulated ATPase activity. This implies that the concentration of Ca2+-ATPase in sarcoplasmic reticulum membranes of fast and slow skeletal or cardiac muscles differs only slightly, and the low Ca2+ transport activity of 'sarcoplasmic reticulum' preparations isolated from slow-twitch skeletal and cardiac muscles is due to the presence of large amount of non-sarcoplasmic-reticulum membrane elements. This is in accord with the relatively small differences in the density of 8.5-nm intramembranous particles seen by freeze-etch electron microscopy in sarcoplasmic reticulum of red and white muscles. The dimensions of the Ca2+-ATPase crystal lattice are similar in sarcoplasmic reticulum membranes of different fiber types; therefore if structural differences exist between 'isoenzymes' of Ca2+-ATPase, these are not reflected in the crystal-lattice.
在无钙培养基中用钒酸钠处理后，肌浆网膜中会形成Ca2+转运ATP酶的晶体阵列[Dux, L.和Martonosi, A. (1983) J. Biol. Chem. 258, 2599 - 2603]。从不同纤维类型（半膜肌、提肛肌、趾长伸肌、膈肌、比目鱼肌和心脏）的大鼠肌肉中分离得到的微粒体制剂中，含有Ca2+ - ATP酶晶体的囊泡比例与Ca2+ - ATP酶含量及Ca2+调节的ATP酶活性密切相关。这意味着快、慢骨骼肌或心肌的肌浆网膜中Ca2+ - ATP酶的浓度差异仅略有不同，从慢肌骨骼肌和心肌中分离得到的“肌浆网”制剂的低Ca2+转运活性是由于存在大量非肌浆网膜成分。这与冷冻蚀刻电子显微镜在红肌和白肌的肌浆网中观察到的8.5 nm膜内颗粒密度相对较小的差异相一致。不同纤维类型的肌浆网膜中Ca2+ - ATP酶晶格的尺寸相似；因此，如果Ca2+ - ATP酶的“同工酶”之间存在结构差异，这些差异在晶格中并未体现出来。
