Research and Teaching Interests
Crystals of PHS
Many important biological processes involved dioxygen, usually requiring the participation of transition metal ions. The primary interest of my research group is the understanding of the fundamental principles of enzyme catalysis, in particular the elucidation of the mechanism of oxygen and substrate activation by metalloenzymes. Our experimental approach includes methodologies from enzymology, molecular biology, physical-organic chemistry, spectroscopy and protein crystallography.
We have begun efforts towards the elucidation of the role of the metal center in the mechanism of group of dioxygenases belonging to the cupin superfamily, including the flavonol 2,3-dioxygenases from Aspergillus flavus and Bacillus subtilis and the acireductone dioxygenase from Klebsiella pneumoniae , members of a small group of enzymes that catalyze the oxidative cleavage of two C-C bonds with concomitant release of CO. We are also studying the copper-conatining enzymes phenoxazinone synthase (PHS) from Streptomyces antibioticus and ammonia monooxygenase (AMO) from Nitrosomonas europaea. PHS is a member of the multicopper oxidases and catalyzes the penultimate step in the synthesis of actinomycin D and AMO catalyzes the difficult oxidation of ammonia to hydroxylamine.
The elucidation of the mechanism of these enzymes should provide important information regarding the role of the metal center in substrate and oxygen activation, the parameters that control electron transfer rates in metalloenzymes and new directions in the design of biomimetic catalysts for alkane activation.
"Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase," M.R. Kumar, A. Zapata, A.J. Ramirez, S.K. Bowen, W.A. Francisco, P.J. Farmer , Proceeding of the National Academy of Sciences USA 47 18926-18931 (2011)
"Structure of phenoxazinone synthase from Streptomyces antibioticus reveals a new type 2 copper center," A.W. Smith, A. Camara-Artigas, M.T. Wang, J.P. Allen, W.A. Francisco, Biochemistry 45 4378-4387 (2006)
"Kinetic and spectroscopic studies on the quercetin 2,3-dioxygenase from Bacillus subtilis," M.R. Schaab, B.M. Barney, W.A. Francisco, Biochemistry 45 1009-1016 (2006)
"Analysis of secreted proteins from Aspergillus flavus," M.L. Medina, P.A. Haynes, L. Breci, W.A. Francisco, Proteomics 5 3153-3161 (2005)
"Characterization of a Small Metal Binding Protein from Nitrosomonas europaea," B.M. Barney, R. LoBrutto and W.A. Francisco, Biochemistry 43 11206-11213 (2004)