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Powell SM, Wang B, Herrera VE, Prather KY, Nguyen NT, Abucayon EG, Thomas LM, Safo MK, Richter-Addo GB. Crystal structural investigations of heme protein derivatives resulting from reactions of aryl- and alkylhydroxylamines with human hemoglobin. J Inorg Biochem 2023; 246:112304. [PMID: 37406385 PMCID: PMC10348690 DOI: 10.1016/j.jinorgbio.2023.112304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 06/10/2023] [Accepted: 06/22/2023] [Indexed: 07/07/2023]
Abstract
Phenylhydroxylamine (PhNHOH) and nitrosobenzene (PhNO) interact with human tetrameric hemoglobin (Hb) to form the nitrosobenzene adduct Hb(PhNO). These interactions also frequently lead to methemoglobin formation in red blood cells. We utilize UV-vis spectroscopy and X-ray crystallography to identify the primary and secondary products that form when PhNHOH and related alkylhydroxylamines (RNHOH; R = Me, t-Bu) react with human ferric Hb. We show that with MeNHOH, the primary product is Hb[α-FeIII(H2O)][β-FeII(MeNO)], in which nitrosomethane is bound to the β subunit but not the α subunit. Attempts to isolate a nitrosochloramphenicol (CAMNO) adduct resulted in our isolation of a Hb[α-FeII][β-FeII-cySOx]{CAMNO} product (cySOx = oxidized cysteine) in which CAMNO was located outside of the protein in the solvent region between the β2 and α2 subunits of the same tetramer. We also observed that the βcys93 residue had been oxidized. In the case of t-BuNHOH, we demonstrate that the isolated product is the β-hemichrome Hb[α-FeIII(H2O)][β-FeIII(His)2]{t-BuNHOH}, in which the β heme has slipped ∼4.4 Å towards the solvent exterior to accommodate the bis-His heme coordination. When PhNHOH is used, a similar β-hemichrome Hb[α-FeIII(H2O)][β-FeIII(His)2-cySOx]{PhNHOH} was obtained. Our results reveal, for the first time, the X-ray structural determination of a β-hemichrome in a human Hb derivative. Our UV-vis and X-ray crystal structural result reveal that although Hb(PhNO) and Hb(RNO) complexes may form as primary products, attempted isolation of these products by crystallization may result in the structural determination of their secondary products which may contain β-hemichromes en route to further protein degradation.
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Affiliation(s)
- Samantha M Powell
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA; Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Bing Wang
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA
| | - Viridiana E Herrera
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA; Department of Chemistry and Physics, Ivory V. Nelson Science Center, Lincoln University, Lincoln University, PA, 19352, USA
| | - Kiana Y Prather
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA; University of Oklahoma College of Medicine, 800 Stanton L. Young Blvd, Oklahoma City, OK 73117, USA
| | - Nancy T Nguyen
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA; University of Oklahoma College of Medicine, 800 Stanton L. Young Blvd, Oklahoma City, OK 73117, USA
| | - Erwin G Abucayon
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA
| | - Leonard M Thomas
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA
| | - Martin K Safo
- Department of Medicinal Chemistry, School of Pharmacy and Institute for Structural Biology, Drug Discovery and Development, Virginia Commonwealth University, 800 East Leigh Street, Richmond, VA 23219, USA
| | - George B Richter-Addo
- Price Family Foundation Institute of Structural Biology, Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA.
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Abucayon EG, Chu JM, Ayala M, Khade RL, Zhang Y, Richter-Addo GB. Insight into the preferential N-binding versus O-binding of nitrosoarenes to ferrous and ferric heme centers. Dalton Trans 2021; 50:3487-3498. [PMID: 33634802 PMCID: PMC8061117 DOI: 10.1039/d0dt03604h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nitrosoarenes (ArNOs) are toxic metabolic intermediates that bind to heme proteins to inhibit their functions. Although much of their biological functions involve coordination to the Fe centers of hemes, the factors that determine N-binding or O-binding of these ArNOs have not been determined. We utilize X-ray crystallography and density functional theory (DFT) analyses of new representative ferrous and ferric ArNO compounds to provide the first theoretical insight into preferential N-binding versus O-binding of ArNOs to hemes. Our X-ray structural results favored N-binding of ArNO to ferrous heme centers, and O-binding to ferric hemes. Results of the DFT calculations rationalize this preferential binding on the basis of the energies of associated spin-states, and reveal that the dominant stabilization forces in the observed ferrous N-coordination and ferric O-coordination are dπ-pπ* and dσ-pπ*, respectively. Our results provide, for the first time, an explanation why in situ oxidation of the ferrous-ArNO compound to its ferric state results in the observed subsequent dissociation of the ligand.
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Affiliation(s)
- Erwin G Abucayon
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA.
| | - Jia-Min Chu
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030, USA.
| | - Megan Ayala
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA.
| | - Rahul L Khade
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030, USA.
| | - Yong Zhang
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030, USA.
| | - George B Richter-Addo
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, USA.
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