Redox-state sensing by hydrogen bonds in the CuA center of cytochrome c oxidase

Abriata, Luciano A.; Vila, Alejandro J.

doi:10.1016/j.jinorgbio.2013.07.032

Cited by 4 publications

(4 citation statements)

References 37 publications

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“…This observation is supported by a series of mutagenesis studies in T1 sites altering this hydrogen bond network. 67 – 71 Since this hydrogen bond is conserved in Cu A scaffolds, 72 the high reduction potential of Az- Tt Cu A , may also be attributed to this feature. The lack of a crystal structure for the latter protein does not allow us to assess in detail the difference between the reduction potential of both chimeras.…”

Section: Discussionmentioning

confidence: 98%

Engineering a bifunctional copper site in the cupredoxin fold by loop-directed mutagenesis

et al. 2018

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Section: Discussionmentioning

confidence: 98%

Engineering a bifunctional copper site in the cupredoxin fold by loop-directed mutagenesis

et al. 2018

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“…The conserved hydrogen bonds include the one (sometimes two) accepted by the sulfur atom of the cysteine residue in mononuclear cupredoxins or its equivalent cysteine in CuA sites (the N-terminal one), and the one donated by the Ne2 atom of the N-terminal histidine to oxygen atoms of carboxylate or amide groups buried inside the protein. All these hydrogen bonds, conserved or not among different cupredoxins, are preserved in the corresponding X-ray structures available for the four apoproteins and make part of large networks [10,31,45], suggesting they could be an integral part of the rack responsible for inducing the entatic state on the copper ions once bound. The conserved hydrogen bonds to the cysteine sulfur are very stable in the four mononuclear cupredoxins, with sulfur-hydrogen distances lower than 3 Å for over 80 % of the simulated time and average values of approximately 2.6 Å .…”

Section: Predefined Arrangements Of the Copper Ligands Are Unstable Imentioning

confidence: 99%

Molecular dynamics simulations of apocupredoxins: insights into the formation and stabilization of copper sites under entatic control

2014

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Cupredoxins perform copper-mediated long-range electron transfer (ET) in biological systems. Their copper-binding sites have evolved to force copper ions into ET-competent systems with decreased reorganization energy, increased reduction potential, and a distinct electronic structure compared with those of non-ET-competent copper complexes. The entatic or rack-induced state hypothesis explains these special properties in terms of the strain that the protein matrix exerts on the metal ions. This idea is supported by X-ray structures of apocupredoxins displaying "closed" arrangements of the copper ligands like those observed in the holoproteins; however, it implies completely buried copper-binding atoms, conflicting with the notion that they must be exposed for copper loading. On the other hand, a recent work based on NMR showed that the copper-binding regions of apocupredoxins are flexible in solution. We have explored five cupredoxins in their "closed" apo forms through molecular dynamics simulations. We observed that prearranged ligand conformations are not stable as the X-ray data suggest, although they do form part of the dynamic landscape of the apoproteins. This translates into variable flexibility of the copper-binding regions within a rigid fold, accompanied by fluctuations of the hydrogen bonds around the copper ligands. Major conformations with solvent-exposed copper-binding atoms could allow initial binding of the copper ions. An eventual subsequent incursion to the closed state would result in binding of the remaining ligands, trapping the closed conformation thanks to the additional binding energy and the fastening of noncovalent interactions that make up the rack.

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“…1,58 Additionally, the high-pH form of met-myoglobin (Mb) has been shown to undergo SCO, where at room temperature it is in a HS state and at lower temperatures it is in a LS ground state (Figure 1C). 59 The influence of distal hydrogen bonding (H-bonding) in Mb, 60–68 hemoglobin, 68–72 cytochrome P450, 73–79 and cytochrome c oxidase 80–85 (C c O) has been examined by experimental (biochemical) and density functional theory (DFT) calculations. Investigations involving biomimetic synthetic models have already contributed and will continue to be key for understanding the influence of distal H-bonding interactions on the behavior of reactive intermediates in enzymatic cycles, for example, ferric superoxo, 57 ferric hydroperoxo, 86–88 and heme-peroxo-copper species.…”

Section: Introductionmentioning

confidence: 99%

“…A spin-state equilibrium also regulates substrate binding and the Fe III/II redox potential in cytochrome P450 monooxygenase (cyt P450), wherein substrate binding drives SCO of Fe III from a LS to HS state, which facilitates one-electron reduction to yield a HS Fe II state, that is necessary to bind O 2 and initiate its catalytic cycle (Figure B). , Additionally, the high-pH form of met-myoglobin (Mb) has been shown to undergo SCO, where at room temperature it is in a HS state and at lower temperatures it is in a LS ground state (Figure C) . The influence of distal hydrogen bonding (H-bonding) in Mb, − hemoglobin, − cytochrome P450, − and cytochrome c oxidase − (C c O) has been examined by experimental (biochemical) and density functional theory (DFT) calculations. Investigations involving biomimetic synthetic models have already contributed and will continue to be key for understanding the influence of distal H-bonding interactions on the behavior of reactive intermediates in enzymatic cycles, for example, ferric superoxo, ferric hydroperoxo, − and heme-peroxo-copper species. ,− …”

Section: Introductionmentioning

confidence: 99%

Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions

et al. 2019

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Synthetic peroxo-bridged high-spin (HS) heme-(μ-η2:η1-O22−)-Cu(L) complexes incorporating (as part of the copper ligand) intramolecular hydrogen-bond (H-bond) capabilities and/or steric effects are herein demonstrated to affect the complex’s electronic and geometric structure, notably impacting the spin state. An H-bonding interaction with the peroxo core favors a low-spin (LS) heme-(μ-η1:η1-O22−)-Cu(L) structure, resulting in a reversible temperature-dependent interconversion of spin state (5 coordinate HS to 6 coordinate LS). The LS state dominates at low temperatures, even in the absence of a strong trans-axial heme ligand. Lewis base addition inhibits the H-bond facilitated spin interconversion by competition for the H-bond donor, illustrating the precise H-bonding interaction required to induce spin-crossover (SCO). Resonance Raman spectroscopy (rR) shows that the H-bonding pendant interacts with the bridging peroxide ligand to stabilize the LS but not the HS state. The H-bond (to the Cu-bound O atom) acts to weaken the O–O bond and strengthen the Fe–O bond, exhibiting ν(M–O) and ν(O–O) values comparable to analogous known LS complexes with a strong donating trans-axial ligand, 1,5-dicyclohexylimidazole, (DCHIm)heme-(μ-η1:η1-O22−)-Cu(L). Variable-temperature (−90 to −130 °C) UV–vis and 2H NMR spectroscopies confirm the SCO process and implicate the involvement of solvent binding. Examining a case of solvent binding without SCO, thermodynamic parameters were obtained from a van’t Hoff analysis, accounting for its contribution in SCO. Taken together, these data provide evidence for the H-bond group facilitating a core geometry change and allowing solvent to bind, stabilizing a LS state. The rR data, complemented by DFT analysis, reveal a stronger H-bonding interaction with the peroxo core in the LS compared to the HS complexes, which enthalpically favors the LS state. These insights enhance our fundamental understanding of secondary coordination sphere influences in metalloenzymes.

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Redox-state sensing by hydrogen bonds in the CuA center of cytochrome c oxidase

Cited by 4 publications

References 37 publications

Engineering a bifunctional copper site in the cupredoxin fold by loop-directed mutagenesis

Engineering a bifunctional copper site in the cupredoxin fold by loop-directed mutagenesis

Molecular dynamics simulations of apocupredoxins: insights into the formation and stabilization of copper sites under entatic control

Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions

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