Tcherkasskaya O, Ptitsyn O B, Knutson J R
Laboratory of Experimental and Computational Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Biochemistry. 2000 Feb 22;39(7):1879-89. doi: 10.1021/bi992117+.
Fluorescence anisotropy kinetics were employed to quantify the nanosecond mobility of tryptophan residues in different conformational states (native, molten globule, unfolded) of apomyoglobins. Of particular interest is the similarity between the fluorescence anisotropy decays of tryptophans in the native and molten globule states. We find that, in these compact states, tryptophan residues rotate rapidly within a cone of semiangle 22-25 degrees and a correlation time of 0.5 ns, in addition to rotating together with the whole protein with a correlation time of 7-11 ns. The similar nanosecond dynamics of tryptophan residues in both states suggests that the conformation changes that distinguish the molten globule and native states of apomyoglobins originate from either subtle, slow rearrangements or fast changes distant from these tryptophans.
利用荧光各向异性动力学来量化脱辅基肌红蛋白不同构象状态（天然态、熔球态、未折叠态）中色氨酸残基的纳秒级迁移率。特别值得关注的是天然态和熔球态色氨酸的荧光各向异性衰减之间的相似性。我们发现，在这些紧密状态下，色氨酸残基除了以7 - 11纳秒的相关时间与整个蛋白质一起旋转外，还在半角为22 - 25度、相关时间为0.5纳秒的圆锥体内快速旋转。两种状态下色氨酸残基相似的纳秒级动力学表明，区分脱辅基肌红蛋白熔球态和天然态的构象变化要么源于细微、缓慢的重排，要么源于远离这些色氨酸的快速变化。
