Linked Life Data

10766788

Source:http://linkedlifedata.com/resource/pubmed/id/10766788

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
16
pubmed:dateCreated
2000-5-10
pubmed:abstractText
The coordination and spin-state of the Corynebacterium diphtheriae heme oxygenase (Hmu O) and the proximal Hmu O H20A mutant have been characterized by UV-visible and resonance Raman (RR) spectrophotometry. At neutral pH the ferric heme-Hmu O complex is a mixture of six-coordinate high spin and six-coordinate low spin species. Changes in the UV-visible and high frequency RR spectra are observed as a function of pH and temperature, with the six-coordinate high spin species being converted to six-coordinate low spin. The low frequency region of the ferrous RR spectrum identified the proximal ligand to the heme as a neutral imidazole with a Fe-His stretching mode at 222 cm(-1). The RR characterization of the heme-CO complex in wt-Hmu O confirms that the proximal imidazole is neither ionized or strongly hydrogen-bonded. Based on sequence identity with the mammalian enzymes the proximal ligand in HO-1 (His-25) and HO-2 (His-45) is conserved (His-20) in the bacterial enzyme. Site-specific mutagenesis identified His-20 as the proximal mutant based on electronic and resonance Raman spectrophotometric analysis. Titration of the heme-Hmu O complex with imidazole restored full catalytic activity to the enzyme, and the coordination of imidazole to the heme was confirmed by RR. However, in the absence of imidazole, the H20A Hmu O mutant was found to catalyze the initial alpha-meso-hydroxylation of the heme. The product of the aerobic reaction was determined to be ferrous verdoheme. Hydrolytic conversion of the verdoheme product to biliverdin concluded that oxidative cleavage of the porphyrin macrocycle was specific for the alpha-meso-carbon. The present data show that, in marked contrast to the human HO-1, the proximal ligand is not essential for the initial alpha-meso-hydroxylation of heme in the C. diphtheriae heme oxygenase-catalyzed reaction.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
275
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11686-92
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:10766788-Bacterial Proteins, pubmed-meshheading:10766788-Biliverdine, pubmed-meshheading:10766788-Carbon Monoxide, pubmed-meshheading:10766788-Catalytic Domain, pubmed-meshheading:10766788-Chromatography, High Pressure Liquid, pubmed-meshheading:10766788-Corynebacterium diphtheriae, pubmed-meshheading:10766788-Electrophoresis, Polyacrylamide Gel, pubmed-meshheading:10766788-Heme, pubmed-meshheading:10766788-Heme Oxygenase (Decyclizing), pubmed-meshheading:10766788-Heme Oxygenase-1, pubmed-meshheading:10766788-Histidine, pubmed-meshheading:10766788-Humans, pubmed-meshheading:10766788-Hydroxylation, pubmed-meshheading:10766788-Ligands, pubmed-meshheading:10766788-Membrane Proteins, pubmed-meshheading:10766788-Models, Chemical, pubmed-meshheading:10766788-Mutagenesis, Site-Directed, pubmed-meshheading:10766788-Oxidation-Reduction, pubmed-meshheading:10766788-Spectrophotometry, Atomic, pubmed-meshheading:10766788-Spectrum Analysis, Raman, pubmed-meshheading:10766788-Structure-Activity Relationship
pubmed:year
2000
pubmed:articleTitle
Identification of the proximal ligand His-20 in heme oxygenase (Hmu O) from Corynebacterium diphtheriae. Oxidative cleavage of the heme macrocycle does not require the proximal histidine.
pubmed:affiliation
Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, USA. awilks@rx.umaryland.edu
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.