Modulation of the Heme Pocket Conformation or Dual Concerted Mechanism upon Substitution of Hydrogen Sulfide by Oxygen Binding to an Unusual Hemoglobin?

Lopez-GarrigaMCB-9974961本研究的目的是研究果胶绿藻血红蛋白(HBI)氧化还原、配体选择和稳定过程的分子基础。这种血红蛋白可能是唯一一种执行其功能的血红素蛋白，以硫化氢结合的铁状态将硫化氢输送到细菌共生体。血红素-Fe+3SH2部分与Gln(E7)基团之间存在氢键是为了稳定HbISH2中心。同样，其他氨基，特别是Gln(E7)、Phe(B10)和Phe(E11)可以与其他HBI配体CO和O2相互作用。为了了解该酶的结构和功能特征，将利用HBI的定点突变体来测定其与不同配体的结合和解离常数随pH的变化。这些研究与FTIR和共振拉曼工作相结合，应该会对控制硫化氢结合、运输和传递的因素产生新的见解。本研究的目的是研究血红素蛋白之间的配基亲和力差异。目前，还不能确定这些差异是由静电效应、空间位阻限制还是氢键差异引起的。希望这些对果胶绿藻血红蛋白I的研究将解决其中的一些问题，并对这种不寻常的血红蛋白的结构和功能特征产生新的见解。这项工作可能会产生对设计具有商业用途的重组HBI蛋白有用的信息，例如，作为特定的硫化氢生物传感器。这些蛋白质还可用于从工业或自然过程中去除有毒的硫化氢，如厌氧发酵、污水和天然气生产。

Lopez-GarrigaMCB-9974961The objective of this research is to investigate the molecular basis for oxidation-reduction, ligand selection, and ligand stabilization processes of hemoglobin (HbI) isolated from Lucina pectinata. This hemoglobin is probably the only heme protein that carries out its function, to transport H2S to a bacteria symbion, in a hydrogen-sulfide bound ferric state. The presence of H-bonding between the heme-Fe+3 SH2 moiety and the Gln(E7) group is postulated to stabilize the HbISH2 center. Likewise, other amino groups, in particular, Gln(E7), Phe(B10), and Phe(E11) may interact with other HbI ligands, CO and O2. In order to understand the structural and functional characteristics of this enzyme, site-directed mutants of HbI will be used to determine its association and dissociation constants with different ligands as a function of pH. These studies in conjunction with the FTIR and resonance Raman work should produce new insight about factors that control H2S binding, transport, and delivery. The goal of this research is to study the ligand affinity differences in heme proteins. At present, it is not established whether these differences arise from electrostatic effects, from steric constraints, or from hydrogen-bonding differences. It is hoped that the these studies with hemoglobin I from Lucina pectinata will resolve some of these issues and produce new insight about the structural and functional characteristics of this unusual hemoglobin. The work is likely to produce information that may be useful in the design of recombinant HbI proteins with commercial uses, for example, as a specific H2S biosensor. These proteins may also be used for the removal of toxic H2S from industrial or natural processes, such as anaerobic fermentation, sewage, and natural gas production.