Fe(II) and α-ketoglutarate-dependent halogenases in natural products biosynthesis

AEI 17

Danica P. Galonic, danica_galonic@hms.harvard.edu1, Sinisa Hrvatin1, Eric W. Barr2, J. Martin Bollinger Jr.2, Carsten Krebs3, and Christopher T. Walsh1. (1) Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Ave, Boston, MA 02115, (2) Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 306 South Frear Building, University Park, PA 16801, (3) Departments of Biochemistry and Molecular Biology and of Chemistry, The Pennsylvania State University, University Park, PA 16802
Halogenation of unactivated carbon centers in the biosynthesis of several compounds of non-ribosomal peptide origin is carried out by a class of mononuclear non-heme iron enzymes that require alpha-ketoglutarate, chloride and oxygen for their activity. Intrigued by their ability to functionalize unactivated methyl groups of the substrate, we carried out kinetic and spectroscopic characterization of chlorination of the gamma-methyl substituent of L-aminobutyric acid attached to the carrier protein CytC2 by iron halogenase CytC3, isolated from soil Streptomyces sp. Through these studies we identified an intermediate state which comprises of two rapidly equilibrating high-spin Fe(IV) complexes that are responsible for the hydrogen atom abstraction from the substrate. The demonstration that the substrate activation proceeds through the C-H-cleaving Fe(IV) intermediate reveals the mechanistic similarity of aliphatic halogenases with related non-heme iron dioxyganeses. Identification of halogenating enzymes in another non-ribosomal peptide gene cluster will also be described.
 

Academic Employment Initiative
8:00 PM-10:00 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Sci-Mix

Academic Employment Initiative

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007