Pennathur-Das R, Vickery L E, Mentzer W, Lubin B H
Biochim Biophys Acta. 1979 Oct 24;580(2):356-65. doi: 10.1016/0005-2795(79)90147-8.
The effect of dimethyl adipimidate, a bifunctional imidoester, on the oxygen affinity of hemoglobin A has been studied. Treatment of human oxyhemoglobin with 5 mM dimethyl adipimidate at pH 8.5, room temperature is accompanied by an increase in oxygen affinity in the presence and absence of 2,3-diphosphoglyceric acid. Circular dichroism measurements in the ultraviolet region indicate that dimethyl adipimidate-treated hemoglobin exhibits a reduced conformational change upon deoxygenation. In order to study the contribution of reacted individual subunits, alpha and beta subunits of dimethyl adipimidate-treated and untreated hemoglobin have been separated and reconstituted to form hybrid tetramers containing either the alpha-treated (alpha t beta c) or the beta-treated subunits (alpha c beta t). Electrophoresis on sodium dodecyl sulfate polyacrylamide gels of isolated alpha and beta globin subunits as well as hybrid tetramers from dimethyl adipimidate-treated hemoglobin reveals that 20% of the globin subunits are cross-linked. In the absence of 2,3-diphosphoglyceric acid, modification of alpha subunits increases the oxygen affinity and reduces the conformational change of the tetramer upon deoxygenation whereas modification of beta subunits has no effect. However, treatment of beta subunits decreases the effect of 2,3-diphosphoglyceric acid on the oxygen affinity of the hybrids and reduces the 2,3-diphosphoglyceric acid-induced spectral changes in oxyhemoglobin. Therefore the interaction of dimethyl adipimidate with both the alpha and beta subunits contributes to regulating the oxygen affinity of human hemoglobin.
已研究了双功能亚氨酯——己二酸二甲酯亚胺对血红蛋白A氧亲和力的影响。在pH 8.5、室温下，用5 mM己二酸二甲酯亚胺处理人氧合血红蛋白，无论有无2,3-二磷酸甘油酸，其氧亲和力都会增加。紫外区域的圆二色性测量表明，经己二酸二甲酯亚胺处理的血红蛋白在脱氧时构象变化减小。为了研究反应的单个亚基的作用，已将经己二酸二甲酯亚胺处理和未处理的血红蛋白的α和β亚基分离并重新组装，以形成含有经α处理的亚基（αtβc）或经β处理的亚基（αcβt）的杂合四聚体。对分离的α和β珠蛋白亚基以及经己二酸二甲酯亚胺处理的血红蛋白的杂合四聚体进行十二烷基硫酸钠聚丙烯酰胺凝胶电泳，结果显示20%的珠蛋白亚基发生了交联。在没有2,3-二磷酸甘油酸的情况下，α亚基的修饰增加了氧亲和力，并减少了四聚体脱氧时的构象变化，而β亚基的修饰则没有影响。然而，β亚基的处理降低了2,3-二磷酸甘油酸对杂合体氧亲和力的影响，并减少了2,3-二磷酸甘油酸诱导的氧合血红蛋白光谱变化。因此，己二酸二甲酯亚胺与α和β亚基的相互作用有助于调节人血红蛋白的氧亲和力。
