Nitrosyl hydride (HNO) as an O2 analogue: long-lived HNO adducts of ferrous globins.
Nitrosyl hydride (HNO) as an O2 analogue: long-lived HNO adducts of ferrous globins.
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DOI：
10.1021/bi900122r
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发表时间：
2009-06-09
期刊：
影响因子：
2.9
通讯作者：
Farmer PJ
中科院分区：
文献类型：
--
作者：
Kumar MR;Pervitsky D;Chen L;Poulos T;Kundu S;Hargrove MS;Rivera EJ;Diaz A;Colón JL;Farmer PJ
Nitrosyl hydride, HNO or nitroxyl, is the one-electron reduced and protonated form of nitric oxide. HNO is isoelectronic to singlet O2, and we have previously reported that deoxy myoglobin traps free HNO to form a stable adduct. In this report, we demonstrate that oxygen-binding hemoglobins from human, soy and clam also trap HNO to form adducts which are stable over a period of weeks. The same species can be formed in higher yield by careful reduction of the ferrous nitrosyl adducts of the proteins. Like the analogous O2-FeII adducts, the HNO adducts are diamagnetic, but with a characteristic HNO resonance in 1H NMR ca. 15 ppm that splits into doublets for H15NO adducts. The 1H and 15N NMR resonances, obtained by HSQC experiments, are shown to differentiate subunits and isoforms of proteins within mixtures. An apparent difference in reduction rates of the NO-adducts of the two subunits of human hemoglobin allows assignment of two distinct nitrosyl hydride peaks by a combination of UVvis, NMR and EPR analysis. The two peaks of HNO-hHb have a persistent 3:1 ratio during trapping reactions, demonstrating a kinetic difference between HNO binding at the two subunits. These results show NMR characterization of ferrous HNO adducts as a unique tool sensitive to structural changes within the oxygen-binding cavity, which may be of use in defining modes of oxygen binding in other heme proteins and enzymes.
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