Vasudevan G, McDonald M J
Department of Chemistry, College of Arts and Sciences, University of Massachusetts, Lowell 01854, USA.
J Protein Chem. 1998 May;17(4):319-27. doi: 10.1023/a:1022551131455.
The kinetics of CNProto- and CNDeutero-hemin binding to apohemoglobin A2 was investigated in a stopped-flow device in 0.05 M potassium phosphate buffer, pH 7, at 10 degrees C. The overall kinetic profile exhibited multiple phases: Phases I-IV corresponding with heme insertion (8.5-13 x 10(7) M(-1) s(-1)), local structural rearrangement (0.21-0.23 s(-1)), global alphadelta structural event (0.071-0.098 s(-1)), and formation of the Fe-His bond (0.009-0.012 s(-1)), respectively. Kinetic differences observed between apohemoglobin A2 and apohemoglobin A (previously studied) prompted an analysis of the structures of beta and delta chains through molecular modeling. This revealed a structural repositioning of the residues not only at, but also distant from the site of the amino acid substitutions, specifically those involved in the heme contact and subunit interface. A significant global change was observed in the structure of the exon-coded 3 region and provided additional evidence for the designation of this as the subunit assembly domain.
在10℃下，于0.05 M磷酸钾缓冲液（pH 7）中，利用停流装置研究了原卟啉氰高铁血红素和氘代卟啉氰高铁血红素与脱辅基血红蛋白A2的结合动力学。整体动力学曲线呈现多个阶段：阶段I-IV分别对应血红素插入（8.5 - 13×10⁷ M⁻¹ s⁻¹）、局部结构重排（0.21 - 0.23 s⁻¹）、整体αδ结构变化（0.071 - 0.098 s⁻¹）以及铁-组氨酸键的形成（0.009 - 0.012 s⁻¹）。观察到脱辅基血红蛋白A2和脱辅基血红蛋白A（先前已研究）之间的动力学差异，促使通过分子建模对β链和δ链的结构进行分析。这揭示了不仅在氨基酸取代位点，而且在远离该位点的残基发生了结构重新定位，特别是那些参与血红素接触和亚基界面的残基。在外显子编码的3区结构中观察到显著的整体变化，为将其指定为亚基组装结构域提供了额外证据。
