Laboratory of Molecular Spectroscopy, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Laboratory of Biophysics and Biomedical Physics, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium.
Dalton Trans. 2023 Mar 7;52(10):2976-2987. doi: 10.1039/d2dt03252j.
Protoglobin from (Pgb) is a dimeric globin belonging to the same lineage of the globin superfamily as globin-coupled sensors. A putative role in the scavenging of reactive nitrogen and oxygen species has been suggested as a possible adaptation mechanism of the host organism to different gaseous environments in the course of evolution. A combination of optical absorption, electronic circular dichroism (ECD), resonance Raman (rRaman), and electron paramagnetic resonance (EPR) reveal the unusual reaction of ferric Pgb with nitrite. In contrast to other globins, a large excess of nitrite did not induce the formation of a nitriglobin form in Pgb. Surprisingly, the addition of nitrite in mildly acidic pH led to the formation of a stable nitric-oxide ligated ferric form of the protein (Pgb-NO). Furthermore, the 300-700 nm ECD spectrum of ferric Pgb is for the first time reported and discussed, showing strong differences in the Soret and Q ellipticity compared to ferric myoglobin, in line with the unusually strongly ruffled haem group of Pgb and the related quantum-mechanical admixture of the = 5/2 and = 3/2 state of its ferric form. The Soret and Q ellipticity change strongly upon formation of Pgb-NO, revealing a significant effect of the nitric-oxide ligation on the haem group and pocket. The related changes in the asymmetric pyrrole half-ring stretching vibration modes observed in the rRaman spectra give experimental support to earlier theoretical models, in which an important role of the in-plane breathing modes of the haem was predicted for the stabilization of the binding of diatomic gases to Pgb.
原肌球蛋白（Pgb）是一种二聚球蛋白，属于球蛋白超家族的同一谱系，与球蛋白偶联传感器相同。有人认为，它在清除活性氮和氧物种方面的作用可能是宿主生物在进化过程中适应不同气体环境的一种机制。光学吸收、电子圆二色性（ECD）、共振拉曼（rRaman）和电子顺磁共振（EPR）的组合揭示了高铁 Pgb 与亚硝酸盐的异常反应。与其他球蛋白不同，高铁 Pgb 与亚硝酸盐的大量过剩不会诱导形成亚硝基球蛋白形式。令人惊讶的是，在轻微酸性 pH 值下添加亚硝酸盐会导致蛋白质（Pgb-NO）形成稳定的一氧化氮配位的高铁形式。此外，首次报道并讨论了高铁 Pgb 的 300-700nm ECD 光谱，与高铁肌红蛋白相比，其 Soret 和 Q 椭圆率表现出强烈的差异，这与 Pgb 异常强烈的起皱血红素基团以及其高铁形式的 = 5/2 和 = 3/2 态的量子力学混合一致。Pgb-NO 形成时 Soret 和 Q 椭圆率发生强烈变化，表明一氧化氮配位对血红素基团和口袋有显著影响。rRaman 光谱中观察到的不对称吡咯半环伸缩振动模式的相关变化为早期理论模型提供了实验支持，其中预测了血红素的面内呼吸模式对稳定二原子气体与 Pgb 结合的重要作用。
