Zhegunov G F, Belous A M
Biokhimiia. 1980 Apr;45(4):687-94.
The structure and functions of the Ca-transport system of sarcoplasmic reticulum (SR) at low temperatures (-5--196 degrees) were studied. It was shown that during SR freezing-thawing the activation energy of ATP enzymatic hydrolysis as well as the Ca-ATPase sensitivity to calcium ions were changed. The Km value for the carrier seemed to be unaffected thereby. Using the EPR method it was shown that after freezing down to -196 degrees and a subsequent thawing the protein-lipil interactions and the orderliness of phospholipid fatty acid chains in the SR membranes were altered. On the contrary, the activity of Ca-ATPase isolated from SR membranes remained unchanged, which is indicative of the enzyme resistance to the cold. The mechanisms responsible for the impairment of the functioning of Ca-transport system of SR membranes due to freezing are discussed.
研究了肌浆网（SR）钙转运系统在低温（-5至-196摄氏度）下的结构和功能。结果表明，在SR冻融过程中，ATP酶水解的活化能以及Ca-ATP酶对钙离子的敏感性发生了变化。载体的Km值似乎未受影响。使用电子顺磁共振（EPR）方法表明，冷冻至-196摄氏度并随后解冻后，SR膜中的蛋白质-脂质相互作用以及磷脂脂肪酸链的有序性发生了改变。相反，从SR膜分离的Ca-ATP酶的活性保持不变，这表明该酶具有抗冻性。讨论了由于冷冻导致SR膜钙转运系统功能受损的机制。
