[Mechanism of Thiocyanate Dehydrogenase Functioning Based on Structural Data]

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Context:

• Thiocyanate dehydrogenase (TCDH) catalyzes the oxidation of thiocyanate to cyanate.
• Previous TCDH structures from Thioalkalivibrio paradoxus had limitations in resolution and data completeness.
• Understanding TCDH mechanism is crucial for bioinorganic chemistry and environmental science.

Purpose:

• To elucidate the high-resolution structure of a gene-modified thiocyanate dehydrogenase from Ptlomicrobium methylotrophicum.
• To investigate the enzyme's active site, copper ion states, and substrate/inhibitor binding.
• To propose a refined mechanism for thiocyanate oxidation based on new structural data.

Summary:

• High-resolution structures of Ptlomicrobium methylotrophicum TCDH reveal two distinct conformations (open and closed active sites) with fully occupied copper ions.
• Superposition of different copper ion oxidation states and ligand coordination within each conformation provides detailed insights.
• Complexes with thiourea and oxygen in the closed conformation facilitate modeling of substrate binding and oxygen activation.

Impact:

• Provides unprecedented atomic-level detail of thiocyanate dehydrogenase structure and function.
• Enables a more accurate understanding of the enzymatic reaction mechanism, including oxygen activation.
• Advances knowledge in bioinorganic chemistry and the catalytic roles of copper enzymes.