Qin B Y, Bewley M C, Creamer L K, Baker H M, Baker E N, Jameson G B
Centre for Structural Biology, Institutes of Fundamental Sciences and Molecular Biosciences, Massey University, Palmerston North, New Zealand.
Biochemistry. 1998 Oct 6;37(40):14014-23. doi: 10.1021/bi981016t.
The structures of the trigonal crystal form of bovine beta-lactoglobulin variant A at pH 6.2, 7.1, and 8.2 have been determined by X-ray diffraction methods at a resolution of 2.56, 2. 24, and 2.49 A, respectively. The corresponding values for R (Rfree) are 0.192 (0.240), 0.234 (0.279), and 0.232 (0.277). The C and N termini as well as two disulfide bonds are clearly defined in these models. The glutamate side chain of residue 89 is buried at pH 6.2 and becomes exposed at pH 7.1 and 8.2. This conformational change, involving the loop 85-90, provides a structural basis for a variety of pH-dependent chemical, physical, and spectroscopic phenomena, collectively known as the Tanford transition.
已分别通过X射线衍射方法在分辨率为2.56埃、2.24埃和2.49埃的条件下测定了牛β-乳球蛋白变体A在pH 6.2、7.1和8.2时三角晶型的结构。R（Rfree）的相应值分别为0.192（0.240）、0.234（0.279）和0.232（0.277）。在这些模型中，C端和N端以及两个二硫键都清晰可辨。89位残基的谷氨酸侧链在pH 6.2时被掩埋，而在pH 7.1和8.2时则暴露出来。这种涉及85 - 90环的构象变化为各种pH依赖的化学、物理和光谱现象提供了结构基础，这些现象统称为坦福德转变。
