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Alanine to serine substitutions drive thermal adaptation in a psychrophilic diatom cytochrome c 6. J Biol Inorg Chem 2020; 25:489-500. [PMID: 32219554 DOI: 10.1007/s00775-020-01777-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 03/16/2020] [Indexed: 10/24/2022]
Abstract
In this study, we investigate the thermodynamic mechanisms by which electron transfer proteins adapt to environmental temperature by directly comparing the redox properties and folding stability of a psychrophilic cytochrome c and a mesophilic homolog. Our model system consists of two cytochrome c6 proteins from diatoms: one adapted specifically to polar environments, the other adapted generally to surface ocean environments. Direct electrochemistry shows that the midpoint potential for the mesophilic homolog is slightly higher at all temperatures measured. Cytochrome c6 from the psychrophilic diatom unfolds with a melting temperature 10.4 °C lower than the homologous mesophilic cytochrome c6. Changes in free energy upon unfolding are identical, within error, for the psychrophilic and mesophilic protein; however, the chemical unfolding transition of the psychrophilic cytochrome c6 is more cooperative than for the mesophilic cytochrome c6. Substituting alanine residues found in the mesophile with serine found in corresponding positions of the psychrophile demonstrates that burial of the polar serine both decreases the thermal stability and decreases the midpoint potential. The mutagenesis data, combined with differences in the m-value of chemical denaturation, suggest that differences in solvent accessibility of the hydrophobic core underlie the adaptation of cytochrome c6 to differing environmental temperature.
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Bialek W, Krzywda S, Zatwarnicki P, Jaskolski M, Kolesinski P, Szczepaniak A. Insights into the relationship between the haem-binding pocket and the redox potential ofc6cytochromes: four atomic resolution structures ofc6andc6-like proteins fromSynechococcussp. PCC 7002. ACTA ACUST UNITED AC 2014; 70:2823-32. [DOI: 10.1107/s1399004714013108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/05/2014] [Indexed: 11/10/2022]
Abstract
The structure of cytochromec6Cfrom the mesophilic cyanobacteriumSynechococcussp. PCC 7002 has been determined at 1.03 Å resolution. This is the first structural report on the recently discovered cyanobacterial cytochromec6-like proteins found in marine and nitrogen-fixing cyanobacteria. Despite high similarity in the overall three-dimensional fold between cytochromesc6andc6C, the latter shows saliently different electrostatic properties in terms of surface charge distribution and dipole moments. Its midpoint redox potential is less than half of the value for typicalc6cytochromes and results mainly from the substitution of one residue in the haem pocket. Here, high-resolution crystal structures of mutants of both cytochromesc6andc6Care presented, and the impact of the mutation of specific residues in the haem-binding pocket on the redox potential is discussed. These findings contribute to the elucidation of the structure–function relationship ofc6-like cytochromes.
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Rousvoal S, Groisillier A, Dittami SM, Michel G, Boyen C, Tonon T. Mannitol-1-phosphate dehydrogenase activity in Ectocarpus siliculosus, a key role for mannitol synthesis in brown algae. PLANTA 2011; 233:261-73. [PMID: 20981555 DOI: 10.1007/s00425-010-1295-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Accepted: 09/26/2010] [Indexed: 05/30/2023]
Abstract
Mannitol represents a major end product of photosynthesis in brown algae (Phaeophyceae), and is, with the β-1,3-glucan laminarin, the main form of carbon storage for these organisms. Despite its importance, little is known about the genes and enzymes responsible for the metabolism of mannitol in these seaweeds. Taking benefit of the sequencing of the Ectocarpus siliculosus genome, we focussed our attention on the first step of the synthesis of mannitol (reduction of the photo-assimilate fructose-6-phosphate), catalysed by the mannitol-1-phosphate dehydrogenase (M1PDH). This activity was measured in algal extracts, and was shown to be regulated by NaCl concentration in the reaction medium. Genomic analysis revealed the presence of three putative M1PDH genes (named EsM1PHD1, EsM1PDH2 and EsM1PDH3). Sequence comparison with orthologs demonstrates the modular architecture of EsM1PHD1 and EsM1PDH2, with an additional N-terminal domain of unknown function. In addition, gene expression experiments carried out on samples harvested through the diurnal cycle, and after several short-term saline and oxidative stress treatments, showed that EsM1PDH1 is the most highly expressed of these genes, whatever the conditions tested. In order to assess the activity of the corresponding protein, this gene was expressed in Escherichia coli. Cell-free extracts prepared from bacteria containing EsM1PDH1 displayed higher M1PDH activity than bacteria transformed with an empty plasmid. Further characterisation of recombinant EsM1PDH1 activity revealed its very narrow substrate specificity, salt regulation, and sensitivity towards an inhibitor of SH-enzymes.
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Affiliation(s)
- Sylvie Rousvoal
- UPMC Univ Paris 6, UMR 7139 Marine Plants and Biomolecules, Station Biologique, 29682 Roscoff, France
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Zander U, Faust A, Klink BU, de Sanctis D, Panjikar S, Quentmeier A, Bardischewsky F, Friedrich CG, Scheidig AJ. Structural basis for the oxidation of protein-bound sulfur by the sulfur cycle molybdohemo-enzyme sulfane dehydrogenase SoxCD. J Biol Chem 2010; 286:8349-8360. [PMID: 21147779 DOI: 10.1074/jbc.m110.193631] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sulfur cycle enzyme sulfane dehydrogenase SoxCD is an essential component of the sulfur oxidation (Sox) enzyme system of Paracoccus pantotrophus. SoxCD catalyzes a six-electron oxidation reaction within the Sox cycle. SoxCD is an α(2)β(2) heterotetrameric complex of the molybdenum cofactor-containing SoxC protein and the diheme c-type cytochrome SoxD with the heme domains D(1) and D(2). SoxCD(1) misses the heme-2 domain D(2) and is catalytically as active as SoxCD. The crystal structure of SoxCD(1) was solved at 1.33 Å. The substrate of SoxCD is the outer (sulfane) sulfur of Cys-110-persulfide located at the C-terminal peptide swinging arm of SoxY of the SoxYZ carrier complex. The SoxCD(1) substrate funnel toward the molybdopterin is narrow and partially shielded by side-chain residues of SoxD(1). For access of the sulfane-sulfur of SoxY-Cys-110 persulfide we propose that (i) the blockage by SoxD-Arg-98 is opened via interaction with the C terminus of SoxY and (ii) the C-terminal peptide VTIGGCGG of SoxY provides interactions with the entrance path such that the cysteine-bound persulfide is optimally positioned near the molybdenum atom. The subsequent oxidation reactions of the sulfane-sulfur are initiated by the nucleophilic attack of the persulfide anion on the molybdenum atom that is, in turn, reduced. The close proximity of heme-1 to the molybdopterin allows easy acceptance of the electrons. Because SoxYZ, SoxXA, and SoxB are already structurally characterized, with SoxCD(1) the structures of all key enzymes of the Sox cycle are known with atomic resolution.
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Affiliation(s)
- Ulrich Zander
- From the Department of Structural Biology, Zoological Institute, Christian-Albrechts-University Kiel, 24118 Kiel, Germany,; the Department of Biophysics-Structural Biology, Saarland University, 66421 Homburg, Germany
| | - Annette Faust
- From the Department of Structural Biology, Zoological Institute, Christian-Albrechts-University Kiel, 24118 Kiel, Germany
| | - Björn U Klink
- the Department of Biophysics-Structural Biology, Saarland University, 66421 Homburg, Germany
| | - Daniele de Sanctis
- the Structural Biology Group, European Synchrotron Radiation Facility Grenoble, 6 Rue Jules Horowitz, B.P. 220, 38043 Grenoble Cedex 9, France, and
| | - Santosh Panjikar
- the EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Armin Quentmeier
- the Fakultät Bio- und Chemieingenieurwesen, Technische Universität Dortmund, Emil-Figge-Strasse 66, 44221 Dortmund, Germany
| | - Frank Bardischewsky
- the Fakultät Bio- und Chemieingenieurwesen, Technische Universität Dortmund, Emil-Figge-Strasse 66, 44221 Dortmund, Germany
| | - Cornelius G Friedrich
- the Fakultät Bio- und Chemieingenieurwesen, Technische Universität Dortmund, Emil-Figge-Strasse 66, 44221 Dortmund, Germany,.
| | - Axel J Scheidig
- From the Department of Structural Biology, Zoological Institute, Christian-Albrechts-University Kiel, 24118 Kiel, Germany,; the Department of Biophysics-Structural Biology, Saarland University, 66421 Homburg, Germany,.
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Bialek W, Krzywda S, Jaskolski M, Szczepaniak A. Atomic-resolution structure of reduced cyanobacterial cytochromec6with an unusual sequence insertion. FEBS J 2009; 276:4426-36. [DOI: 10.1111/j.1742-4658.2009.07150.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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