title: Electronic properties of the highly ruffled heme bound to the heme degrading enzyme IsdI.
abstract: IsdI, a heme-degrading protein from Staphylococcus aureus, binds heme in a manner that distorts the normally planar heme prosthetic group to an extent greater than that observed so far for any other heme-binding protein. To understand better the relationship between this distinct structural characteristic and the functional properties of IsdI, spectroscopic, electrochemical, and crystallographic results are reported that provide evidence that this heme ruffling is essential to the catalytic activity of the protein and eliminates the need for the water cluster in the distal heme pocket that is essential for the activity of classical heme oxygenases. The lack of heme orientational disorder in (1)H-NMR spectra of the protein argues that the catalytic formation of β- and δ-biliverdin in nearly equal yield results from the ability of the protein to attack opposite sides of the heme ring rather than from binding of the heme substrate in two alternative orientations.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia Centre for Blood Research, Life Sciences Centre, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
authors.forename: Shin-ichi J
authors.initials: SJ
authors.lastname: Takayama
authors.forename: Georgia
authors.initials: G
authors.lastname: Ukpabi
authors.forename: Michael E P
authors.initials: ME
authors.lastname: Murphy
authors.forename: A Grant
authors.initials: AG
authors.lastname: Mauk
mesh_terms: D000042:Absorption; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003486:Cyanides / Q000378:metabolism; D055664:Electrochemical Techniques; D004583:Electrons; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D003486:Cyanides; D006418:Heme; D007501:Iron; C497164:IsdI protein, Staphylococcus aureus; D006899:Mixed Function Oxygenases