Galinato Mary Grace I, Fogle Robert S, Stetz Amanda, Galan Jhenny F
School of Science-Chemistry, Penn State Erie, The Behrend College, Erie, PA 16563, United States.
School of Science-Chemistry, Penn State Erie, The Behrend College, Erie, PA 16563, United States.
J Inorg Biochem. 2016 Jan;154:7-20. doi: 10.1016/j.jinorgbio.2015.10.010. Epub 2015 Oct 22.
Globins, such as hemoglobin (Hb) and myoglobin (Mb), have gained attention for their ability to reduce nitrite (NO2(-)) to nitric oxide (NO). The molecular interactions that regulate this chemistry are not fully elucidated, therefore we address this issue by investigating one part of the active site that may control this reaction. Here, the effects of the 2,4-heme substituents on the nitrite reductase (NiR) reaction, and on the structures and energies of the ferrous nitrite intermediates, are investigated using Mb as a model system. This is accomplished by studying Mbs with hemes that have different 2,4-R groups, namely diacetyldeuteroMb (-acetyl), protoMb (wild-type (wt) Mb, -vinyl), deuteroMb (-H), and mesoMb (-ethyl). While trends on the natural charge on Fe and O-atom of bound nitrite are observed among the series of Mbs, the Fe(II)-NPyr (Pyr=pyrrole) and Fe(II)-NHis93 (His=histidine) bond lengths do not significantly change. Kinetic analysis shows increasing NiR activity as follows: diacetyldeuteroMb<wt Mb<deuteroMb<mesoMb. Nitrite binding energy calculations of the different Mb(II)-nitrite conformations demonstrate the N-bound complexes to be more stable than the O-bound complexes for all the different types of heme structures, with diacetyldeuteroMb having the greatest nitrite binding affinity. Spectral deconvolution on the final product generated from the reaction between Mb(II) and NO2(-) for the reconstituted Mbs indicates the formation of 1:1 Mb(III) and Mb(II)-NO. The electronic changes induced by the -R groups on the 2,4-positions do not alter the stoichiometric ratio of the products, resembling wt Mb.
珠蛋白，如血红蛋白（Hb）和肌红蛋白（Mb），因其将亚硝酸盐（NO2(-)）还原为一氧化氮（NO）的能力而受到关注。调节这种化学反应的分子相互作用尚未完全阐明，因此我们通过研究活性位点中可能控制该反应的一部分来解决这个问题。在这里，以Mb作为模型系统，研究了2,4-血红素取代基对亚硝酸还原酶（NiR）反应以及对亚铁亚硝酸盐中间体的结构和能量的影响。这是通过研究具有不同2,4-R基团的血红素的Mbs来实现的，即二乙酰氘代肌红蛋白（-乙酰基）、原肌红蛋白（野生型（wt）Mb，-乙烯基）、氘代肌红蛋白（-H）和中肌红蛋白（-乙基）。虽然在一系列Mbs中观察到结合亚硝酸盐的Fe和O原子上的自然电荷趋势，但Fe(II)-NPyr（Pyr = 吡咯）和Fe(II)-NHis93（His = 组氨酸）键长没有显著变化。动力学分析表明NiR活性增加如下：二乙酰氘代肌红蛋白<wt Mb<氘代肌红蛋白<中肌红蛋白。不同Mb(II)-亚硝酸盐构象的亚硝酸盐结合能计算表明，对于所有不同类型的血红素结构，N结合的复合物比O结合的复合物更稳定，二乙酰氘代肌红蛋白具有最大的亚硝酸盐结合亲和力。对重组Mbs的Mb(II)与NO2(-)反应生成的最终产物进行光谱解卷积表明形成了1:1的Mb(III)和Mb(II)-NO。2,4-位上的-R基团引起的电子变化不会改变产物的化学计量比，类似于wt Mb。
