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de Oliveira Silva YR, Zheng D, Peters SC, Fisher OS. Stabilization of a Cu-binding site by a highly conserved tryptophan residue. J Inorg Biochem 2024; 253:112501. [PMID: 38342077 DOI: 10.1016/j.jinorgbio.2024.112501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 01/31/2024] [Accepted: 02/01/2024] [Indexed: 02/13/2024]
Abstract
Copper serves as an essential cofactor for nearly all living organisms. There are still many gaps remaining in our knowledge of how Gram-positive bacteria import copper and maintain homeostasis. To obtain a better understanding of how these processes work, here we focus on the ycnKJI operon responsible for regulating copper levels in the Gram-positive bacterium Bacillus subtilis. This operon encodes three Cu-related proteins: a copper-dependent transcriptional repressor (YcnK), a putative copper importer (YcnJ), and a copper-binding protein of unknown function (YcnI). We previously found that YcnI's extracellular Domain of Unknown Function 1775 (DUF1775) houses a monohistidine brace motif that coordinates a single Cu(II) ion. The Cu(II) binding site includes a highly conserved tryptophan residue. Here, we investigate the role of that tryptophan and the ability of the protein to interact with other oxidation states of Cu. We find that YcnI exhibits strong preference for binding Cu in the oxidized Cu(II) state, and that the conserved tryptophan residue is not essential for the interaction. We determine the structure of a tryptophan variant to 1.95 Å resolution that indicates that the tryptophan is needed to stabilize the metal binding interaction, and find that this variant has weaker affinity for Cu(II) than the wild-type protein. Together, these data provide further insights into the DUF1775 domain family and reveal the role of the conserved tryptophan residue.
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Affiliation(s)
| | - Dia Zheng
- Department of Chemistry, Lehigh University, 6 E Packer Ave, Bethlehem, PA 18015, USA
| | - Stephen C Peters
- Department of Earth and Environmental Sciences, Lehigh University, 1 W Packer Ave, Bethlehem, PA 18015, USA
| | - Oriana S Fisher
- Department of Chemistry, Lehigh University, 6 E Packer Ave, Bethlehem, PA 18015, USA.
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Roger M, Leone P, Blackburn NJ, Horrell S, Chicano TM, Biaso F, Giudici-Orticoni MT, Abriata LA, Hura GL, Hough MA, Sciara G, Ilbert M. Beyond the coupled distortion model: structural analysis of the single domain cupredoxin AcoP, a green mononuclear copper centre with original features. Dalton Trans 2024; 53:1794-1808. [PMID: 38170898 PMCID: PMC10804444 DOI: 10.1039/d3dt03372d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 11/30/2023] [Indexed: 01/05/2024]
Abstract
Cupredoxins are widely occurring copper-binding proteins with a typical Greek-key beta barrel fold. They are generally described as electron carriers that rely on a T1 copper centre coordinated by four ligands provided by the folded polypeptide. The discovery of novel cupredoxins demonstrates the high diversity of this family, with variations in terms of copper-binding ligands, copper centre geometry, redox potential, as well as biological function. AcoP is a periplasmic cupredoxin belonging to the iron respiratory chain of the acidophilic bacterium Acidithiobacillus ferrooxidans. AcoP presents original features, including high resistance to acidic pH and a constrained green-type copper centre of high redox potential. To understand the unique properties of AcoP, we undertook structural and biophysical characterization of wild-type AcoP and of two Cu-ligand mutants (H166A and M171A). The crystallographic structures, including native reduced AcoP at 1.65 Å resolution, unveil a typical cupredoxin fold. The presence of extended loops, never observed in previously characterized cupredoxins, might account for the interaction of AcoP with physiological partners. The Cu-ligand distances, determined by both X-ray diffraction and EXAFS, show that the AcoP metal centre seems to present both T1 and T1.5 features, in turn suggesting that AcoP might not fit well to the coupled distortion model. The crystal structures of two AcoP mutants confirm that the active centre of AcoP is highly constrained. Comparative analysis with other cupredoxins of known structures, suggests that in AcoP the second coordination sphere might be an important determinant of active centre rigidity due to the presence of an extensive hydrogen bond network. Finally, we show that other cupredoxins do not perfectly follow the coupled distortion model as well, raising the suspicion that further alternative models to describe copper centre geometries need to be developed, while the importance of rack-induced contributions should not be underestimated.
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Affiliation(s)
- Magali Roger
- CNRS, Aix-Marseille University, Bioenergetic and Protein Engineering Laboratory, BIP UMR 7281, Mediterranean Institute of Microbiology, 13009 Marseille, France.
| | - Philippe Leone
- CNRS, Aix-Marseille University, Laboratoire d'Ingénierie des Systèmes Macromoléculaires, LISM UMR7255, 13009 Marseille, France
| | - Ninian J Blackburn
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, Oregon 97239, USA
| | - Sam Horrell
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Tadeo Moreno Chicano
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Frédéric Biaso
- CNRS, Aix-Marseille University, Bioenergetic and Protein Engineering Laboratory, BIP UMR 7281, Mediterranean Institute of Microbiology, 13009 Marseille, France.
| | - Marie-Thérèse Giudici-Orticoni
- CNRS, Aix-Marseille University, Bioenergetic and Protein Engineering Laboratory, BIP UMR 7281, Mediterranean Institute of Microbiology, 13009 Marseille, France.
| | - Luciano A Abriata
- Laboratory for Biomolecular Modeling and Protein Purification and Structure Core Facility, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Greg L Hura
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Lab, Berkeley, CA, USA
| | - Michael A Hough
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Giuliano Sciara
- CNRS, Aix-Marseille University, Bioenergetic and Protein Engineering Laboratory, BIP UMR 7281, Mediterranean Institute of Microbiology, 13009 Marseille, France.
- Aix Marseille Univ, INRAE, BBF UMR1163, Biodiversité et Biotechnologie Fongiques, 13288 Marseille, France
| | - Marianne Ilbert
- CNRS, Aix-Marseille University, Bioenergetic and Protein Engineering Laboratory, BIP UMR 7281, Mediterranean Institute of Microbiology, 13009 Marseille, France.
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Mammoser CC, LeMasters BE, Edwards SG, McRae EM, Mullins MH, Wang Y, Garcia NM, Edmonds KA, Giedroc DP, Thielges MC. The structure of plastocyanin tunes the midpoint potential by restricting axial ligation of the reduced copper ion. Commun Chem 2023; 6:175. [PMID: 37612467 PMCID: PMC10447441 DOI: 10.1038/s42004-023-00977-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 08/07/2023] [Indexed: 08/25/2023] Open
Abstract
Blue copper proteins are models for illustrating how proteins tune metal properties. Nevertheless, the mechanisms by which the protein controls the metal site remain to be fully elucidated. A hindrance is that the closed shell Cu(I) site is inaccessible to most spectroscopic analyses. Carbon deuterium (C-D) bonds used as vibrational probes afford nonperturbative, selective characterization of the key cysteine and methionine copper ligands in both redox states. The structural integrity of Nostoc plastocyanin was perturbed by disrupting potential hydrogen bonds between loops of the cupredoxin fold via mutagenesis (S9A, N33A, N34A), variably raising the midpoint potential. The C-D vibrations show little change to suggest substantial alteration to the Cu(II) coordination in the oxidized state or in the Cu(I) interaction with the cysteine ligand. They rather indicate, along with visible and NMR spectroscopy, that the methionine ligand distinctly interacts more strongly with the Cu(I) ion, in line with the increases in midpoint potential. Here we show that the protein structure determines the redox properties by restricting the interaction between the methionine ligand and Cu(I) in the reduced state.
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Affiliation(s)
- Claire C Mammoser
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Brynn E LeMasters
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Department of Chemistry, University of Wisconsin, Madison, WI, 53706, USA
| | - Sydney G Edwards
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Emma M McRae
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - M Hunter Mullins
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Yiqi Wang
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Nicholas M Garcia
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- University of Wisconsin School of Medicine and Public Health, Madison, WI, 53726, USA
| | - Katherine A Edmonds
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - David P Giedroc
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Megan C Thielges
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA.
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