caa a22 4500 605507228 CHVBK 20210128100631.0 cr unu---uuuuu 210128e20151001xx s 000 0 eng 10.1007/s00775-015-1296-9 doi (NATIONALLICENCE)springer-10.1007/s00775-015-1296-9 Density functional theory calculations on the active site of biotin synthase: mechanism of S transfer from the Fe2S2 cluster and the role of 1st and 2nd sphere residues [Elektronische Daten] [Atanu Rana, Subal Dey, Amita Agrawal, Abhishek Dey] Density functional theory (DFT) calculations are performed on the active site of biotin synthase (BS) to investigate the sulfur transfer from the Fe2S2 cluster to dethiobiotin (DTB). The active site is modeled to include both the 1st and 2nd sphere residues. Molecular orbital theory considerations and calculation on smaller models indicate that only an S atom (not S2−) transfer from an oxidized Fe2S2 cluster leads to the formation of biotin from the DTB using two adenosyl radicals generated from S-adenosyl-l-methionine. The calculations on larger protein active site model indicate that a 9-monothiobiotin bound reduced cluster should be an intermediate during the S atom insertion from the Fe2S2 cluster consistent with experimental data. The Arg260 bound to Fe1, being a weaker donor than cysteine bound to Fe2, determines the geometry and the electronic structure of this intermediate. The formation of this intermediate containing the C9-S bond is estimated to have a ΔG≠ of 17.1kcal/mol while its decay by the formation of the 2nd C6-S bond is calculated to have a ΔG≠ of 29.8kcal/mol, i.e. the 2nd C-S bond formation is calculated to be the rate determining step in the cycle and it leads to the decay of the Fe2S2 cluster. Significant configuration interaction (CI), present in these transition states, helps lower the barrier of these reactions by~30-25kcal/mol relative to a hypothetical outer-sphere reaction. The conserved Phe285 residue near the Fe2S2 active site determines the stereo selectivity at the C6 center of this radical coupling reaction. Graphical Abstract: Reaction mechanism of BS investigated using DFT calculations. Strong CI and the Phe285 residue control the kinetic rate and stereochemistry of the product. SBIC, 2015 Biotin biosynthesis nationallicence Cofactor nationallicence Iron-sulfur cluster nationallicence Structure-function relationship nationallicence Density functional theory nationallicence Electronic structure nationallicence Rana Atanu Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut Dey Subal Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut Agrawal Amita Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut Dey Abhishek Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut JBIC Journal of Biological Inorganic Chemistry Springer Berlin Heidelberg 20/7(2015-10-01), 1147-1162 0949-8257 20:7<1147 2015 20 775 https://doi.org/10.1007/s00775-015-1296-9 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00775-015-1296-9 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Rana Atanu Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut NATIONALLICENCE 700 1- Dey Subal Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut NATIONALLICENCE 700 1- Agrawal Amita Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut NATIONALLICENCE 700 1- Dey Abhishek Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 700032, Kolkata, West Bengal, India aut NATIONALLICENCE 773 0- JBIC Journal of Biological Inorganic Chemistry Springer Berlin Heidelberg 20/7(2015-10-01), 1147-1162 0949-8257 20:7<1147 2015 20 775