Structure of the flavocytochrome c sulfide dehydrogenase associated with the copper‐binding protein CopC from the haloalkaliphilic sulfur‐oxidizing bacterium Thioalkalivibrio paradoxusARh 1

• Published in: Acta crystallographica. Section D, Biological crystallography. Biological crystallography., 2018-07, Vol.74 (7), p.632-642
• Main Authors: Osipov, Eugeny M., Lilina, Anastasia V., Tsallagov, Stanislav I., Safonova, Tatyana N., Sorokin, Dimitry Y., Tikhonova, Tamara V., Popov, Vladimir O.
• Format: Article
• Language: English
• Subjects: Affinity; Amino Acid Sequence; Bacterial Proteins - chemistry; Binding Sites; Carrier Proteins - chemistry; Complex formation; CopC; Copper; Copper compounds; copper‐binding protein; Crystallization; Cytochrome c Group - chemistry; Dehydrogenases; Flavin; flavocytochrome c sulfide dehydrogenase; Haem; Metabolism; Oxidation; Oxidoreductases - chemistry; Protein Conformation; Protein structure; Proteins; protein–protein complex; Sulfide; Sulfur; Thioalkalivibrio paradoxus; Thiobacillus - chemistry; Thiocyanates; X-Ray Diffraction; X‐ray structure
• ISSN: 2059-7983; 0907-4449; 2059-7983; 1399-0047
• DOI: 10.1107/S2059798318005648

Flavocytochrome c sulfide dehydrogenase from Thioalkalivibrio paradoxus (TpFCC) is a heterodimeric protein consisting of flavin‐ and monohaem c‐binding subunits. TpFCC was co‐purified and co‐crystallized with the dimeric copper‐binding protein TpCopC. The structure of the TpFCC–(TpCopC)2 complex was determined by X‐ray diffraction at 2.6 Å resolution. The flavin‐binding subunit of TpFCC is structurally similar to those determined previously, and the structure of the haem‐binding subunit is similar to that of the N‐terminal domain of dihaem FCCs. According to classification based on amino‐acid sequence, TpCopC belongs to a high‐affinity CopC subfamily characterized by the presence of a conserved His1‐Xxx‐His3 motif at the N‐terminus. Apparently, a unique α‐helix which is present in each monomer of TpCopC at the interface with TpFCC plays a key role in complex formation. The structure of the copper‐binding site in TpCopC is similar to those in other known CopC structures. His3 is not involved in binding to the copper ion and is 6–7 Å away from this ion. Therefore, the His1‐Xxx‐His3 motif cannot be considered to be a key factor in the high affinity of CopC for copper(II) ions. It is suggested that the TpFCC–(TpCopC)2 heterotetramer may be a component of a large periplasmic complex that is responsible for thiocyanate metabolism. The structure of the monohaem flavocytochrome c sulfide dehydrogenase co‐purified and co‐crystallized with the copper‐binding protein CopC was solved and refined to 2.6 Å resolution.