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Jenner LP, Crack JC, Kurth JM, Soldánová Z, Brandt L, Sokol KP, Reisner E, Bradley JM, Dahl C, Cheesman MR, Butt JN. Reaction of Thiosulfate Dehydrogenase with a Substrate Mimic Induces Dissociation of the Cysteine Heme Ligand Giving Insights into the Mechanism of Oxidative Catalysis. J Am Chem Soc 2022; 144:18296-18304. [PMID: 36173876 PMCID: PMC9562282 DOI: 10.1021/jacs.2c06062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Thiosulfate dehydrogenases are bacterial cytochromes
that contribute
to the oxidation of inorganic sulfur. The active sites of these enzymes
contain low-spin c-type heme with Cys–/His axial ligation. However, the reduction potentials of these hemes
are several hundred mV more negative than that of the thiosulfate/tetrathionate
couple (Em, +198 mV), making it difficult
to rationalize the thiosulfate oxidizing capability. Here, we describe
the reaction of Campylobacter jejuni thiosulfate dehydrogenase (TsdA) with sulfite, an analogue of thiosulfate.
The reaction leads to stoichiometric conversion of the active site
Cys to cysteinyl sulfonate (Cα-CH2-S-SO3–) such that the protein exists in a form
closely resembling a proposed intermediate in the pathway for thiosulfate
oxidation that carries a cysteinyl thiosulfate (Cα-CH2-S-SSO3–). The active
site heme in the stable sulfonated protein displays an Em approximately 200 mV more positive than the Cys–/His-ligated state. This can explain the thiosulfate
oxidizing activity of the enzyme and allows us to propose a catalytic
mechanism for thiosulfate oxidation. Substrate-driven release of the
Cys heme ligand allows that side chain to provide the site of substrate
binding and redox transformation; the neighboring heme then simply
provides a site for electron relay to an appropriate partner. This
chemistry is distinct from that displayed by the Cys-ligated hemes
found in gas-sensing hemoproteins and in enzymes such as the cytochromes
P450. Thus, a further class of thiolate-ligated hemes is proposed,
as exemplified by the TsdA centers that have evolved to catalyze the
controlled redox transformations of inorganic oxo anions of sulfur.
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Affiliation(s)
- Leon P Jenner
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Julia M Kurth
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Zuzana Soldánová
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Linda Brandt
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Katarzyna P Sokol
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, CambridgeCB2 1EW, United Kingdom
| | - Erwin Reisner
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, CambridgeCB2 1EW, United Kingdom
| | - Justin M Bradley
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Myles R Cheesman
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Julea N Butt
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
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A noncanonical cytochrome c stimulates calcium binding by PilY1 for type IVa pili formation. Proc Natl Acad Sci U S A 2022; 119:2115061119. [PMID: 35121662 PMCID: PMC8833165 DOI: 10.1073/pnas.2115061119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/28/2021] [Indexed: 12/23/2022] Open
Abstract
Type IVa pili (T4aP) are versatile bacterial cell surface structures that undergo extension/adhesion/retraction cycles powered by the cell envelope-spanning T4aP machine. In this machine, a complex composed of four minor pilins and PilY1 primes T4aP extension and is also present at the pilus tip mediating adhesion. Similar to many several other bacteria, Myxococcus xanthus contains multiple minor pilins/PilY1 sets that are incompletely understood. Here, we report that minor pilins and PilY1 (PilY1.1) of cluster_1 form priming and tip complexes contingent on calcium and a noncanonical cytochrome c (TfcP) with an unusual His/Cys heme ligation. We provide evidence that TfcP is unlikely to participate in electron transport and instead stimulates calcium binding by PilY1.1 at low-calcium concentrations, thereby stabilizing PilY1.1 and enabling T4aP function in a broader range of calcium concentrations. These results not only identify a previously undescribed function of cytochromes c but also illustrate how incorporation of an accessory factor expands the environmental range under which the T4aP system functions.
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