title: The active site structure of E. coli HPII catalase. Evidence favoring coordination of a tyrosinate proximal ligand to the chlorin iron.
abstract: E. coli produces 2 catalases known as HPI and HPII. While the heme prosthetic group of the HPII catalase has been established to be a dihydroporphyrin or chlorin, the identity of the proximal ligand to the iron has not been addressed. The magnetic circular dichroism (MCD) spectrum of native ferric HPII catalase is very similar to those of a 5-coordinate phenolate-ligated ferric chlorin complex, a model for tyrosinate proximal ligation, as well as of chlorin-reconstituted ferric horseradish peroxidase, a model for 5-coordinate histidine ligation. However, further MCD comparisons of chlorin-reconstituted myoglobin with parallel ligand-bound adducts of the catalase clearly rule out histidine ligation in the latter, leaving tyrosinate as the best candidate for the proximal ligand.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208.
authors.forename: J H
authors.initials: JH
authors.lastname: Dawson
authors.forename: A M
authors.initials: AM
authors.lastname: Bracete
authors.forename: A M
authors.initials: AM
authors.lastname: Huff
authors.forename: S
authors.initials: S
authors.lastname: Kadkhodayan
authors.forename: C M
authors.initials: CM
authors.lastname: Zeitler
authors.forename: M
authors.initials: M
authors.lastname: Sono
authors.forename: C K
authors.initials: CK
authors.lastname: Chang
authors.forename: P C
authors.initials: PC
authors.lastname: Loewen
mesh_terms: D001665:Binding Sites; D002374:Catalase / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology*; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D011166:Porphyrins; D011487:Protein Conformation; D014443:Tyrosine
chemical_list: D007527:Isoenzymes; D011166:Porphyrins; C006969:chlorin; D014443:Tyrosine; D002374:Catalase