Edelstein S J
Département de Biochimie, Université de Genève, Switzerland.
J Mol Biol. 1996 Apr 12;257(4):737-44. doi: 10.1006/jmbi.1996.0198.
The two-state (MWC) model for cooperative oxygen binding by tetrameric (alpha2beta2) hemoglobin based on concerted transitions between symmetric states (T and R) is extended to include a third, asymmetric state with one alphabeta dimer possessing high (R-like) oxygen affinity and the other alphabeta possessing low (T-like) oxygen affinity. The asymmetric state is assigned a stability that corresponds to the level reported by Ackers and colleagues in the studies on mixed valence hybrids that led to their proposed "molecular code for cooperativity in hemoglobin." However, this level of stability for the asymmetric intermediates significantly diminishes cooperativity in simulated oxygenation curves, to a degree (Hill n = 2.1) that is no longer compatible with the well-established oxygenation properties of normal ferrous hemoglobin (Hill n approximately 3.0). Therefore, the cyanomet derivatives do not appear to be reliable analogues of intermediate oxygenation states.
基于对称状态（T态和R态）之间的协同转变，由四聚体（α2β2）血红蛋白进行协同氧结合的双态（MWC）模型被扩展，以纳入第三种不对称状态，即一个αβ二聚体具有高（类似R态）氧亲和力，另一个αβ二聚体具有低（类似T态）氧亲和力。赋予这种不对称状态的稳定性与阿克斯及其同事在关于混合价杂合体的研究中所报告的水平相对应，这些研究促使他们提出了“血红蛋白协同性的分子编码”。然而，这种不对称中间体的稳定性水平在模拟氧合曲线中显著降低了协同性，降至（希尔系数n = 2.1）不再与正常亚铁血红蛋白已确立的氧合特性（希尔系数n约为3.0）相符的程度。因此，氰化高铁衍生物似乎并非中间氧合状态的可靠类似物。
