Dux L, Papp S, Martonosi A
J Biol Chem. 1985 Nov 5;260(25):13454-8.
Trypsin cleaves the Ca2+-ATPase of sarcoplasmic reticulum into two major fragments (A and B), followed by subsequent cleavage into smaller peptides. Although the ATP-dependent Ca2+ transport is still observed after cleavage of the ATPase into the A and B fragments, the Ca2+ transport energized by acetyl phosphate is strongly inhibited. Covalent labeling of the Ca2+-ATPase by fluorescein 5'-isothiocyanate inhibited both the ATP and acetyl phosphate-dependent Ca2+ transport. Vanadate protected the A and B fragments from further hydrolysis and preserved the ability of the cleaved Ca2+-ATPase to form crystals and to show the characteristic conformational changes in response to Ca2+ and EGTA that are observed with the intact enzyme. The protective effect of vanadate may be useful for the isolation of the A and B fragments in functional form.
胰蛋白酶将肌浆网的Ca2+ -ATP酶裂解为两个主要片段（A和B），随后进一步裂解为更小的肽段。尽管在ATP酶裂解为A和B片段后仍可观察到ATP依赖性的Ca2+转运，但由乙酰磷酸驱动的Ca2+转运受到强烈抑制。用异硫氰酸荧光素5'-对Ca2+ -ATP酶进行共价标记，抑制了ATP和乙酰磷酸依赖性的Ca2+转运。钒酸盐可保护A和B片段不被进一步水解，并保留裂解后的Ca2+ -ATP酶形成晶体的能力，以及呈现出与完整酶所观察到的对Ca2+和乙二醇双四乙酸（EGTA）响应的特征性构象变化的能力。钒酸盐的保护作用可能有助于以功能形式分离A和B片段。
