Holmes M A, Le Trong I, Turley S, Sieker L C, Stenkamp R E
Department of Biological Structure, University of Washington, Seattle 98195.
J Mol Biol. 1991 Apr 5;218(3):583-93. doi: 10.1016/0022-2836(91)90703-9.
The crystallographic structure analyses of deoxy and oxy hemerythrin have been carried out at 2.0 A resolution to extend the low resolution views of the physiological forms of this oxygen-binding protein. Restrained least-squares refinement has produced molecular models giving R-values of 16.8% for deoxy (41,064 reflections from 10 A to 2.0 A) and 17.3% for oxy hemerythrin (40,413 reflections from 10.0 A to 2.0 A). The protein structure in each derivative is very similar to that of myohemerythrin and the various met forms of hemerythrin. The binuclear complex in each derivative retains an oxygen atom bridging the two iron atoms, but the bond lengths found in deoxy hemerythrin support the idea that, in that form, the bridge is protonated, i.e. the bridging group is a hydroxyl. Dioxygen binds to the pentaco-ordinate iron atom in deoxy hemerythrin in the conversion to oxy hemerythrin. The interatomic distances are consistent with the proposed mechanism where the proton from the bridging group is transferred to the bound dioxygen, stabilizing it in the peroxo oxidation state by forming a hydrogen bond between the peroxy group and the bridging oxygen atom.
已在2.0埃分辨率下对脱氧和氧合蚯蚓血红蛋白进行了晶体结构分析，以扩展对这种氧结合蛋白生理形式的低分辨率观察。约束最小二乘精修得到了分子模型，脱氧蚯蚓血红蛋白（10埃至2.0埃的41,064个反射）的R值为16.8%，氧合蚯蚓血红蛋白（10.0埃至2.0埃的40,413个反射）的R值为17.3%。每个衍生物中的蛋白质结构与肌蚯蚓血红蛋白和蚯蚓血红蛋白的各种变价形式非常相似。每个衍生物中的双核配合物保留了一个桥接两个铁原子的氧原子，但在脱氧蚯蚓血红蛋白中发现的键长支持了这样一种观点，即该形式下桥是质子化的，即桥接基团是一个羟基。在向氧合蚯蚓血红蛋白转化过程中，双氧与脱氧蚯蚓血红蛋白中的五配位铁原子结合。原子间距离与提出的机制一致，即桥接基团中的质子转移到结合的双氧上，通过在过氧基团和桥接氧原子之间形成氢键使其稳定在过氧氧化态。
