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Gardner PR. Ordered Motions in the Nitric-Oxide Dioxygenase Mechanism of Flavohemoglobin and Assorted Globins with Tightly Coupled Reductases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1414:45-96. [PMID: 36520413 DOI: 10.1007/5584_2022_751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nitric-oxide dioxygenases (NODs) activate and combine O2 with NO to form nitrate. A variety of oxygen-binding hemoglobins with associated partner reductases or electron donors function as enzymatic NODs. Kinetic and structural investigations of the archetypal two-domain microbial flavohemoglobin-NOD have illuminated an allosteric mechanism that employs selective tunnels for O2 and NO, gates for NO and nitrate, transient O2 association with ferric heme, and an O2 and NO-triggered, ferric heme spin crossover-driven, motion-controlled, and dipole-regulated electron-transfer switch. The proposed mechanism facilitates radical-radical coupling of ferric-superoxide with NO to form nitrate while preventing suicidal ferrous-NO formation. Diverse globins display the structural and functional motifs necessary for a similar allosteric NOD mechanism. In silico docking simulations reveal monomeric erythrocyte hemoglobin alpha-chain and beta-chain intrinsically matched and tightly coupled with NADH-cytochrome b5 oxidoreductase and NADPH-cytochrome P450 oxidoreductase, respectively, forming membrane-bound flavohemoglobin-like mammalian NODs. The neuroprotective neuroglobin manifests a potential NOD role in a close-fitting ternary complex with membrane-bound NADH-cytochrome b5 oxidoreductase and cytochrome b5. Cytoglobin interfaces weakly with cytochrome b5 for O2 and NO-regulated electron-transfer and coupled NOD activity. The mechanistic model also provides insight into the evolution of O2 binding cooperativity in hemoglobin and a basis for the discovery of allosteric NOD inhibitors.
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Gardner AM, Gardner PR. Allostery in the nitric oxide dioxygenase mechanism of flavohemoglobin. J Biol Chem 2020; 296:100186. [PMID: 33310705 PMCID: PMC7948479 DOI: 10.1074/jbc.ra120.016637] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 12/12/2022] Open
Abstract
The substrates O2 and NO cooperatively activate the NO dioxygenase function of Escherichia coli flavohemoglobin. Steady-state and transient kinetic measurements support a structure-based mechanistic model in which O2 and NO movements and conserved amino acids at the E11, G8, E2, E7, B10, and F7 positions within the globin domain control activation. In the cooperative and allosteric mechanism, O2 migrates to the catalytic heme site via a long hydrophobic tunnel and displaces LeuE11 away from the ferric iron, which forces open a short tunnel to the catalytic site gated by the ValG8/IleE15 pair and LeuE11. NO permeates this tunnel and leverages upon the gating side chains triggering the CD loop to furl, which moves the E and F-helices and switches an electron transfer gate formed by LysF7, GlnE7, and water. This allows FADH2 to reduce the ferric iron, which forms the stable ferric–superoxide–TyrB10/GlnE7 complex. This complex reacts with internalized NO with a bimolecular rate constant of 1010 M−1 s−1 forming nitrate, which migrates to the CD loop and unfurls the spring-like structure. To restart the cycle, LeuE11 toggles back to the ferric iron. Actuating electron transfer with O2 and NO movements averts irreversible NO poisoning and reductive inactivation of the enzyme. Together, structure snapshots and kinetic constants provide glimpses of intermediate conformational states, time scales for motion, and associated energies.
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Affiliation(s)
- Anne M Gardner
- Research and Development Division, Miami Valley Biotech, Dayton, Ohio, USA; Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Paul R Gardner
- Research and Development Division, Miami Valley Biotech, Dayton, Ohio, USA; Division of Critical Care Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA; Chemistry and Biochemistry Department, University of Dayton, Dayton, Ohio, USA.
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Seiwert N, Heylmann D, Hasselwander S, Fahrer J. Mechanism of colorectal carcinogenesis triggered by heme iron from red meat. Biochim Biophys Acta Rev Cancer 2019; 1873:188334. [PMID: 31783067 DOI: 10.1016/j.bbcan.2019.188334] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/25/2019] [Accepted: 11/25/2019] [Indexed: 02/07/2023]
Abstract
Colorectal cancer (CRC) is one of the major tumor entities worldwide, with an increasing incidence in younger people. CRC formation is causally linked to various genetic, life-style and dietary risk factors. Among the ladder, the consumption of red meat has emerged as important risk factor contributing to CRC. A large body of evidence shows that heme iron is the critical component of red meat, which promotes colorectal carcinogenesis. In this review, we describe the uptake and cellular fate of both heme and inorganic iron in intestinal epithelial cells. Next, an overview on the DNA damaging properties of heme iron is provided, highlighting the DNA adducts relevant for CRC etiology. Moreover, heme triggered mechanisms leading to colonic hyperproliferation are presented, which are intimately linked to changes in the intestinal microbiota induced by heme. A special focus was set on the impact of heme iron on innate and adaptive immune cells, which could be relevant in the context of CRC. Finally, we recapitulate in vivo studies providing evidence for the tumor-promoting potential of dietary heme iron. Altogether, heme iron affects numerous key pathways involved in the pathogenesis of CRC.
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Affiliation(s)
- Nina Seiwert
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany; Rudolf Buchheim Institute of Pharmacology, Justus Liebig University Giessen, 35392 Giessen, Germany; Division of Food Chemistry and Toxicology, Department of Chemistry, Technical University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Daniel Heylmann
- Rudolf Buchheim Institute of Pharmacology, Justus Liebig University Giessen, 35392 Giessen, Germany
| | | | - Jörg Fahrer
- Department of Toxicology, University Medical Center Mainz, 55131 Mainz, Germany; Rudolf Buchheim Institute of Pharmacology, Justus Liebig University Giessen, 35392 Giessen, Germany; Division of Food Chemistry and Toxicology, Department of Chemistry, Technical University of Kaiserslautern, 67663 Kaiserslautern, Germany.
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Lushington GH, Barnes AC. Protein Glycation: An Old Villain is Shedding Secrets. Comb Chem High Throughput Screen 2019; 22:362-369. [DOI: 10.2174/1386207322666190704094356] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 05/02/2019] [Accepted: 06/10/2019] [Indexed: 01/16/2023]
Abstract
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The glycation of proteins is non-physiological post-translational incorporation of
carbohydrates onto the free amines or guanidines of proteins and some lipids. Although the
existence of glycated proteins has been known for forty years, a full understanding of their
pathogenic nature has been slow in accruing. In recent years, however, glycation has gained widespread
acceptance as a contributing factor in numerous metabolic, autoimmune, and neurological
disorders, tying together several confounding aspects of disease etiology. From diabetes, arthritis,
and lupus, to multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer’s, and Parkinson’s
diseases, an emerging glycation/inflammation paradigm now offers significant new insight into a
physiologically important toxicological phenomenon. It exposes novel drug targets and treatment
options, and may even lay foundations for long-awaited breakthroughs.
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This ‘current frontier’ article briefly profiles current knowledge regarding the underlying causes
of glycation, the structural biology implications of such modifications, and their pathological
consequences. Although several emerging therapeutic strategies for addressing glycation
pathologies are introduced, the primary purpose of this mini-review is to raise awareness of the
challenges and opportunities inherent in this emerging new medicinal target area.
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Li R, Dai X, Feng Z, Li Y, Zhao M, Liu J, Li H, Chen Y, Ma Y, Tang Y. Effect of toxic ligands on O 2 binding to heme and their toxicity mechanism. Phys Chem Chem Phys 2019; 21:14957-14963. [PMID: 31236551 DOI: 10.1039/c9cp02583a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Heme, as the cofactor and active site of Hb, enables Hb to carry out the necessary function required for O2 management for life, that is, reversible O2 binding for transport. In this paper, the microscopic mechanism of heme-associated poisoning has been elucidated from the perspective of electronic interaction by performing first-principles calculations. The results show that the functional groups (-CHO, -COOH, -NO2, -NH2) and CN exhibit a stronger affinity for heme than O2 and are more likely to occupy the O2 binding site, which results in the loss of the ability of heme to carry O2. Moreover, the addition of functional groups, CO and CN to heme at the side site can cause a pronounced enhancement toward the O2 binding characteristics of heme, which prevents heme from releasing O2 to oxygen-consuming tissues as the blood circulates. The reversible O2 binding function of heme is disrupted by the presence of these toxic ligands in the heme binding pocket, which greatly affects O2 transport in the blood. The inability of tissues to obtain O2 leads to tissue hypoxia, which is the main cause of poisoning. Based on the energy, geometry and electronic properties, the hypoxia mechanism proposed by us coincides well with experiment, and the research has the potential to provide a theoretical reference for the relevant areas of bioscience.
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Affiliation(s)
- Renyi Li
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Xianqi Dai
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Zhen Feng
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Yi Li
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Mingyu Zhao
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Jing Liu
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Huiting Li
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Yang Chen
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Yaqiang Ma
- College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China.
| | - Yanan Tang
- Quantum Materials Research Center, College of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou 450044, China.
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Abstract
Metformin elicits pleiotropic effects that are beneficial for treating diabetes, as well as particular cancers and aging. In spite of its importance, a convincing and unifying mechanism to explain how metformin operates is lacking. Here we describe investigations into the mechanism of metformin action through heme and hemoprotein(s). Metformin suppresses heme production by 50% in yeast, and this suppression requires mitochondria function, which is necessary for heme synthesis. At high concentrations comparable to those in the clinic, metformin also suppresses heme production in human erythrocytes, erythropoietic cells and hepatocytes by 30–50%; the heme-targeting drug artemisinin operates at a greater potency. Significantly, metformin prevents oxidation of heme in three protein scaffolds, cytochrome c, myoglobin and hemoglobin, with Kd values < 3 mM suggesting a dual oxidation and reduction role in the regulation of heme redox transition. Since heme- and porphyrin-like groups operate in diverse enzymes that control important metabolic processes, we suggest that metformin acts, at least in part, through stabilizing appropriate redox states in heme and other porphyrin-containing groups to control cellular metabolism.
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