4V2K
Crystal structure of the thiosulfate dehydrogenase TsdA in complex with thiosulfate
Summary for 4V2K
| Entry DOI | 10.2210/pdb4v2k/pdb |
| Descriptor | THIOSULFATE DEHYDROGENASE, HEME C, THIOSULFATE, ... (4 entities in total) |
| Functional Keywords | oxidoreductase, cytochrome c, his/cys heme, disulfide formation, cysteine modification |
| Biological source | ALLOCHROMATIUM VINOSUM |
| Total number of polymer chains | 1 |
| Total formula weight | 28407.53 |
| Authors | Grabarczyk, D.B.,Chappell, P.E.,Eisel, B.,Johnson, S.,Lea, S.M.,Berks, B.C. (deposition date: 2014-10-10, release date: 2015-02-18, Last modification date: 2024-11-06) |
| Primary citation | Grabarczyk, D.B.,Chappell, P.E.,Eisel, B.,Johnson, S.,Lea, S.M.,Berks, B.C. Mechanism of Thiosulfate Oxidation in the Soxa Family of Cysteine-Ligated Cytochromes J.Biol.Chem., 290:9209-, 2015 Cited by PubMed Abstract: Thiosulfate dehydrogenase (TsdA) catalyzes the oxidation of two thiosulfate molecules to form tetrathionate and is predicted to use an unusual cysteine-ligated heme as the catalytic cofactor. We have determined the structure of Allochromatium vinosum TsdA to a resolution of 1.3 Å. This structure confirms the active site heme ligation, identifies a thiosulfate binding site within the active site cavity, and reveals an electron transfer route from the catalytic heme, through a second heme group to the external electron acceptor. We provide multiple lines of evidence that the catalytic reaction proceeds through the intermediate formation of a S-thiosulfonate derivative of the heme cysteine ligand: the cysteine is reactive and is accessible to electrophilic attack; cysteine S-thiosulfonate is formed by the addition of thiosulfate or following the reverse reaction with tetrathionate; the S-thiosulfonate modification is removed through catalysis; and alkylating the cysteine blocks activity. Active site amino acid residues required for catalysis were identified by mutagenesis and are inferred to also play a role in stabilizing the S-thiosulfonate intermediate. The enzyme SoxAX, which catalyzes the first step in the bacterial Sox thiosulfate oxidation pathway, is homologous to TsdA and can be inferred to use a related catalytic mechanism. PubMed: 25673696DOI: 10.1074/JBC.M114.618025 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.29 Å) |
Structure validation
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