Ariki M, Magde D, Lanyi J K
J Biol Chem. 1987 Apr 15;262(11):4947-51.
Laser-excited luminescence lifetimes of lanthanide ions bound to bacteriorhodopsin have been measured in deionized membranes. The luminescence titration curve, as well as the binding curve of apomembrane (retinal-free) with Eu3+, has shown that the removal of the retinal does not significantly affect the affinity of Eu3+ for the two high affinity sites of bacteriorhodopsin. The D2O effects on decay rate constants indicate that Eu3+ bound to the high affinity sites of native membrane or apomembrane is coordinated by about six ligands in the first coordination sphere. Tb3+ is shown to be coordinated by four ligands. The data indicate that metal ions bind to the protein with a specific geometry. From intermetal energy transfer experiments using Eu3+-Pr3+, Tb3+-Ho3+, and Tb3+-Er3+, the distance between the two high affinity sites is estimated to be 7-8 A.
已在去离子化膜中测量了与细菌视紫红质结合的镧系离子的激光激发发光寿命。发光滴定曲线以及脱辅基膜（无视黄醛）与Eu3+的结合曲线表明，视黄醛的去除不会显著影响Eu3+对细菌视紫红质两个高亲和力位点的亲和力。D2O对衰变速率常数的影响表明，与天然膜或脱辅基膜的高亲和力位点结合的Eu3+在第一配位层中由大约六个配体配位。已表明Tb3+由四个配体配位。数据表明金属离子以特定的几何结构与蛋白质结合。通过使用Eu3+-Pr3+、Tb3+-Ho3+和Tb3+-Er3+的金属间能量转移实验，估计两个高亲和力位点之间的距离为7-8埃。
