Calander Home 2001-2002 2002-2003 Matthew B. Neibergall Structural Basis for the Regulation of O2 Binding and Reactivity by the Redox State of a Remote 2Fe-2S cluster in Rieske Dioxygenases Date: March 3 Time: Noon to 1 Place: BSBE 4-101 Rieske dioxygenase enzymes catalyze the cis-dihydroxylation of aromatic substrates using a mononuclear nonheme iron active site and a Rieske-type 2Fe-2S cluster. Typically, 2Fe-2S clusters supply electrons to the active site during catalysis but are not directly involved in the transformation of substrate to product. Previous work demonstrated that O2 binding and activation are regulated by the oxidation state of the Rieske cluster in naphthalene 1,2-dioxygenase (NDO) and benzoate 1,2-dioxygenase (Wolfe et al, J. Biol. Chem. (2001) 276:1945-53). The X-ray structure of NDO shows that the Rieske cluster is 12 ? from the active site (Kauppi et al, Structure (1998) 6:571-86). Recent work by Cosper et al (Protein Science (2002) 11:2969-2973) and Yang et al (J. Am. Chem. Soc. (2003) 125: 2034-35) provide new insight into the structural basis for this redox-dependent regulation.