Crystal Structure of Biotin Synthase, an S-Adenosylmethionine-Dependent Radical Enzyme

摘要

The crystal structure of biotin synthase from Escherichia coli in complex with S-adenosyl-L-methionine and dethiobiotin has been determined to 3.4 angstrom resolution. This structure addresses how "AdoMet radical" or "radical SAM" enzymes use Fe_4S_4 clusters and S-adenosyl-L-methionine to generate organic radicals. Biotin synthase catalyzes the radical-mediated insertion of sulfur into dethiobiotin to form biotin. The structure places the substrates between the Fe_4S_4 cluster, essential for radical generation, and the Fe_2S_2 cluster, postulated to be the source of sulfur, with both clusters in unprecedented coordination environments.