Protonation of the oxo-bridged heme/copper assemblies: Modeling the oxidized state of the cytochrome c oxidase active site
- UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
- Shabnam Hematian, Assistant Professor (Creator)
- Firoz Shah Tuglak Khan, Postdoctoral Research Associate (Creator)
- Institution
- The University of North Carolina at Greensboro (UNCG )
- Web Site: http://library.uncg.edu/
Abstract: In this study on model compounds for the resting oxidized state of the iron copper binuclear center in cytochrome c oxidase (CcO), we describe the synthesis of a new µ-oxo-heme/Cu complex, [(TPP)FeIII–O–CuII(tmpa)][B(C6F5)4] (2) {TPP: tetraphenyl porphyrinate(2–); TMPA: tris(2-pyridylmethylamine)}, as well as two protonation events for three µ-oxo-heme/Cu complexes with varying peripheral substituents on the heme site. The addition of increasing amounts of strong acid to these µ-oxo-heme/Cu systems successively led to the generation of the corresponding µ-hydroxo, µ-aquo, and the dissociated complexes. The heme/Cu assemblies bridged through a water ligand are reported here for the first time and the 1H NMR and 19F NMR spectral properties are consistent with antiferromagnetically coupled high-spin iron(III) and copper(II) centers. By titration using a series of protonated amines, the pKa values for the corresponding µ-hydroxo-heme/Cu species (i.e., the first protonation event) have been reported and compared with the pKa ranges previously estimated for related systems. These synthetic systems may represent structural models for the oxidized FeIII–X–CuII resting state, or turnover intermediates and can be employed to clarify the nature of proton/electron transfer events in CcO. Synopsis: The resting oxidized state of the cytochrome c oxidase active site contains an Fea3-OHx-CuB moiety. Here, we investigated two successive protonation events, for a series of µ-oxo-heme/Cu assemblies and reported the pKa values for the first protonation event. The µ-aquo-heme/Cu complexes described here are the first examples of such systems.
Protonation of the oxo-bridged heme/copper assemblies: Modeling the oxidized state of the cytochrome c oxidase active site
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Created on 5/2/2022
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Additional Information
- Publication
- Journal of Inorganic Biochemistry 225, 111593. https://doi.org/10.1016/j.jinorgbio.2021.111593
- Language: English
- Date: 2021
- Keywords
- cytochrome c oxidase, bridging ligand, protonation, acid dissociation constant, paramagnetic NMR, antiferromagnetic coupling