1. Allosteric Cooperativity in Proton Energy Conversion in A1-Type Cytochrome c Oxidase
- Author
-
Giuseppe Capitanio, Sergio Papa, Luigi Leonardo Palese, and Francesco Papa
- Subjects
Conformational change ,Stereochemistry ,Respiratory chain ,Cooperativity ,Heme ,Crystallography, X-Ray ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,Electron Transport ,Electron Transport Complex IV ,03 medical and health sciences ,chemistry.chemical_compound ,Allosteric Regulation ,Structural Biology ,Cytochrome c oxidase ,Electrochemical gradient ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,Binding Sites ,biology ,Cytochrome c ,Proton Pumps ,0104 chemical sciences ,Oxygen ,Heme A ,chemistry ,biology.protein ,Protons ,Protein Binding - Abstract
Cytochrome c oxidase (CcO), the CuA, heme a, heme a3, CuB enzyme of respiratory chain, converts the free energy released by aerobic cytochrome c oxidation into a membrane electrochemical proton gradient (ΔμH+). ΔμH+ derives from the membrane anisotropic arrangement of dioxygen reduction to two water molecules and transmembrane proton pumping from a negative (N) space to a positive (P) space separated by the membrane. Spectroscopic, potentiometric, and X-ray crystallographic analyses characterize allosteric cooperativity of dioxygen binding and reduction with protonmotive conformational states of CcO. These studies show that allosteric cooperativity stabilizes the favorable conformational state for conversion of redox energy into a transmembrane ΔμH+. (i) Dioxygen binding to Fea3 at BNC selects a CcO state in which the conformation of the subunit I-helix X, next in sequence to the hemes a and a3 histidine axial ligands, opens access of pumped protons from the N space to a Mg2+-storage site at the opposite (P) membrane side. (ii) Sequential electron transfer at CuA and heme a is associated with additional CcO conformational change in which protons are translocated from the Mg2+-site to the propionate(s) of heme a. From there, protons are expelled in the P space on heme a oxidation by electrostatic repulsion along a hydrogen bond network of amino acid residues and/or structured water molecules.
- Published
- 2020