Structure/Function of Respiratory Hemoproteins

描述（由申请人提供）：血红蛋白（Hb）在生物氧化中起着核心作用，它有效地将重要氧化剂O2从肺输送到组织，并将代谢的主要废物之一CO2从组织输送到肺。因此，了解Hb调控其功能的分子机制具有重要的生物医学意义。长期以来，Monod, Wyman, and Changeux （MWC）和Perutz的两态变构模型一直被认为是生理条件下O2与Hb协同结合的各种结构和功能数据的最合理的描述。最近在该基金的支持下进行的工作挑战了MWC/Perutz模型的基本假设，即Hb的O2亲和力主要由T/R四级结构转变控制。在我们实验室进行的工作表明，需要一个新的“全局变构”模型来充分考虑在异向变构效应物存在下观察到的氧化性质的大变化。这种“全局变构”模型提出，Hb在T（脱氧）和R（氧）状态下与异向变构效应物相互作用所引起的三级结构变化主要调节Hb的功能，如O2亲和性、协同性和玻尔效应。本提案旨在利用热力学、动力学、量热、光谱、结构和计算技术，基于“全局变构”模型研究Hb的分子功能，以建立Hb中协同性和变构的可行分子机制，从全局角度解释Hb的功能行为。Hb变构的分子机制的阐明无疑将有助于我们进一步了解在代谢过程的控制和调节中起重要作用的变构酶的机制。

DESCRIPTION (provided by applicant): Hemoglobin (Hb) plays a central role in biological oxidation by efficiently transporting O2, the vital oxidant, from the lung to the tissues and CO2, one of the major waste products of metabolism, from the tissues to the lung. Thus, understanding the molecular mechanism of how Hb regulates its functions is of biomedical significance. The two-state allosteric model of Monod, Wyman, and Changeux (MWC) and Perutz has been long considered the most plausible description of a wide variety of structural and functional data on the cooperative O2 binding to Hb under physiological conditions. Recent work performed under the auspices of this grant has challenged the fundamental assumption of the MWC/Perutz model, namely, that the O2 affinity of Hb is primarily controlled by the T/R quaternary structural transition. Work performed in our laboratory shows that a new "global allostery" model is required to fully account for the large variations of oxygenation properties observed in the presence of heterotropic allosteric effectors. This "global allostery" model proposes that the tertiary structural changes induced by the interactions of Hb in both T (deoxy) and R (oxy) states with heterotropic allosteric effectors primarily modulate functions of Hb such as the O2 affinity, cooperativity, and Bohr effect. This proposal aims at investigating the molecular functions of Hb based upon the "global allostery" model using thermodynamic, kinetic, calorimetric, spectroscopic, structural, and computational techniques in order to establish a viable molecular mechanism for cooperativity and allostery in Hb that explains the functional behavior of Hb from a global viewpoint. Elucidation of the molecular mechanism of allostery of Hb will undoubtedly contribute to our further understanding of the mechanisms of allosteric enzymes which play vital roles in the control and regulation of metabolic processes.