Influence of the Protein Matrix on Intramolecular Histidine Ligation in Ferric and Ferrous Hexacoordinate Hemoglobins.
From: Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA.
Proteins
- Publish Date: Jan 2007
- ISSN: 1097-0134
- Volume: 66
- Issue: 1
- Pages: 172-82
- Medium: Internet
- Language: English
- Citation (JAMA): Halder Puspita, Trent James T, Hargrove Mark S, et al. Influence of the Protein Matrix on Intramolecular Histidine Ligation in Ferric and Ferrous Hexacoordinate Hemoglobins.. Proteins Jan 2007;66:172-82
Abstract
Present in most organisms, hexacoordinate hemoglobins (hxHbs) are proteins that have evolved the capacity for reversible bis-histidyl heme coordination. The heme prosthetic group enables diverse protein functionality, such as electron transfer, redox reactions, ligand transport, and enzymatic catalysis. The reactivity of heme is greatly effected by the coordination and noncovalent chemical environment imposed by its connate protein. Of considerable interest is how the hxHb globin fold achieves reversible intramolecular coordination while still enabling high-affinity binding of oxygen, nitric oxide, and other small ligands. Here we explore this question by examining the role of the protein matrix on coordination behavior in a group of hxHbs from animals, plants, and bacteria, including human neuroglobin and cytoglobin, a nonsymbiotic hemoglobin from rice, and a truncated hemoglobin from the cyanobacterium Synechocystis. This is done with a set of experiments measuring the reduction potentials of each wild-type hxHb and its corresponding mutant protein where the reversibly bound histidine (the distal His) has been replaced with a noncoordinating side chain. These reduction potentials, coupled with studies of the mutant proteins saturated with exogenous imidazole, enable us to assess the effects of the protein matrices on histidine coordination. Our results show significant variation among the hxHbs, demonstrating flexibility in the globin moiety’s ability to regulate reversible coordination. This regulation is particularly evident in the plant nonsymbiotic hemoglobins, where ferric state histidine coordination affinity is substantially lowered by the protein matrix.
Mesh Headings (Keywords): Animals, Bacterial Proteins, Binding Sites, Ferric Compounds, Ferrous Compounds, Globins, Hemoglobins, Histidine, Humans, Imidazoles, Ligands, Models, Molecular, Nerve Tissue Proteins, Plant Proteins, Synechocystis, Thermodynamics, Truncated Hemoglobins
Check for Full Text / PubMed Unique Identifier (PMID): 17044063
This abstract is part of PubMed, a service of the U.S. National Library of Medicine. PubMed includes more than 17 million citations from MEDLINE and other life science journals for biomedical articles. See Copyright and Disclaimers.
Linked medical terms appearing on this page are added by Healia to help readers find more information and are not part of the original PubMed document.
The data herein was last updated on July 8th, 2008 and may not reflect the most current and accurate data available from NLM.