Klemens M R, Grisham C M
Department of Chemistry, University of Virginia, Charlottesville 22901.
Biochem Biophys Res Commun. 1988 Aug 30;155(1):236-42. doi: 10.1016/s0006-291x(88)81074-x.
At least four of the intermediate states of Ca2+-ATPase (and presumably ion transport) can be trapped and characterized using water proton relaxation measurements. Gd3+ binds to two occluded Ca2+ transport sites on Ca2+-ATPase which have a low accessibility to solvent water. In the presence of the MgATP analogue Co(NH3)4AMPPCP, a new state for bound Gd3+ with one less water of hydration) is observed. In the presence of Co(NH3)4ATP or ATP, two additional states for bound Gd3+ are detected by NMR, the first of which probably represents an intermediate state of ATP hydrolysis. The latter is the most occluded Gd3+ site yet observed in these studies and corresponds to the highly occluded E1-P state observed with CrATP (Vilsen and Andersen, Biochim. Biophys. Acta 898, 313 (1987).
利用水质子弛豫测量，至少可以捕获并表征四种Ca2+-ATP酶的中间状态（可能还有离子转运状态）。Gd3+与Ca2+-ATP酶上两个被封闭的Ca2+转运位点结合，这些位点对溶剂水的可及性较低。在MgATP类似物Co(NH3)4AMPPCP存在的情况下，观察到一种结合Gd3+的新状态（水合水少一个）。在Co(NH3)4ATP或ATP存在的情况下，通过核磁共振检测到另外两种结合Gd3+的状态，其中第一种可能代表ATP水解的中间状态。后者是这些研究中观察到的最封闭的Gd3+位点，对应于用CrATP观察到的高度封闭的E1-P状态（维尔森和安德森，《生物化学与生物物理学学报》898, 313 (1987)）。
