Froud R J, Lee A G
Biochem J. 1986 Jul 1;237(1):197-206. doi: 10.1042/bj2370197.
We have studied the fluorescence of the Ca2+ + Mg2+-activated ATPase of sarcoplasmic reticulum labelled with fluorescein isothiocyanate. The change in intensity of fluorescein fluorescence caused by addition of Ca2+ to the labelled ATPase can be interpreted in terms of a two-conformation model for the ATPase, one conformation (E1) having a high affinity for Ca2+, the other (E2) a low affinity. Effects of Ca2+ as a function of pH allow an estimate of the effect of pH on the E1/E2 ratio, consistent with kinetic studies. A model is presented for binding of Ca2+ to the ATPase as a function of pH that is consistent both with the data on the E1/E2 equilibrium and with literature data on Ca2+ binding.
我们研究了用异硫氰酸荧光素标记的肌浆网Ca2+ + Mg2+激活的ATP酶的荧光。向标记的ATP酶中添加Ca2+所引起的荧光素荧光强度变化,可以用ATP酶的双构象模型来解释,一种构象(E1)对Ca2+具有高亲和力,另一种(E2)对Ca2+具有低亲和力。Ca2+作为pH函数的效应可以估算pH对E1/E2比率的影响,这与动力学研究结果一致。提出了一个Ca2+作为pH函数与ATP酶结合的模型,该模型与E1/E2平衡数据以及关于Ca2+结合的文献数据均相符。