Beatty E J, Cox M C, Frenkiel T A, He Q Y, Mason A B, Sadler P J, Tucker A, Woodworth R C
Department of Chemistry, Birbeck College, University of London, UK.
Protein Eng. 1997 May;10(5):583-91. doi: 10.1093/protein/10.5.583.
The conserved Trp residue within helix 5 of the N-lobe of human serum transferrin (hTF/2N, 40 kDa) has been mutated to Tyr. NMR and CD spectra and energy calculations show that the mutation causes little perturbation of the overall structure of hTF/2N although the chelating agent Tiron removed Fe3+ from the mutant protein about three times faster than from wild-type hTF/2N. 1H-NMR resonances of residues in the Leu122-Trp128-Ile132 hydrophobic patch are assigned both by ring current calculations and with the aid of the mutation. [1H, 15N]-NMR resonances for 11 of the 14 Tyr residues were observed in the spectra of 15N-Tyr-hTF/2N and a resonance for Tyr128 was assignable in spectra of the mutant. The 15N resonance of Y128 was sensitive to oxalate and Ga3+ binding, and Ga3+ binding perturbed 15N resonances for most of the Tyr residues. Since these are well distributed over the N-lobe, it can be concluded that metal-induced structural changes are not merely local to the binding site.
人血清转铁蛋白（hTF/2N，40 kDa）N叶螺旋5内保守的色氨酸残基已突变为酪氨酸。核磁共振（NMR）和圆二色（CD）光谱以及能量计算表明，尽管螯合剂钛铁试剂从突变蛋白中去除Fe3+的速度比从野生型hTF/2N中快约三倍，但该突变对hTF/2N的整体结构几乎没有干扰。通过环流计算并借助该突变对Leu122-Trp128-Ile132疏水区域中残基的1H-NMR共振进行了归属。在15N-酪氨酸-hTF/2N的光谱中观察到了14个酪氨酸残基中11个的[1H, 15N]-NMR共振，并且在突变体的光谱中可归属Tyr128的一个共振。Y128的15N共振对草酸盐和Ga3+结合敏感，并且Ga3+结合使大多数酪氨酸残基的15N共振发生扰动。由于这些酪氨酸残基在N叶上分布良好，可以得出结论，金属诱导的结构变化不仅仅局限于结合位点。
