| 1. |
- Andersson, Charlotta S, et al.
(författare)
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A Mycobacterium tuberculosis ligand-binding Mn/Fe protein reveals a new cofactor in a remodeled R2-protein scaffold
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:14, s. 5633-8
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Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis R2c is the prototype for a recently discovered group of ribonucleotide reductase R2 proteins that use a heterodinuclear Mn/Fe redox cofactor for radical generation and storage. Here, we show that the Mycobacterium tuberculosis protein Rv0233, an R2 homologue and a potential virulence factor, contains the heterodinuclear manganese/iron-carboxylate cofactor but displays a drastic remodeling of the R2 protein scaffold into a ligand-binding oxidase. The first structural characterization of the heterodinuclear cofactor shows that the site is highly specific for manganese and iron in their respective positions despite a symmetric arrangement of coordinating residues. In this protein scaffold, the Mn/Fe cofactor supports potent 2-electron oxidations as revealed by an unprecedented tyrosine-valine crosslink in the active site. This wolf in sheep's clothing defines a distinct functional group among R2 homologues and may represent a structural and functional counterpart of the evolutionary ancestor of R2s and bacterial multicomponent monooxygenases.
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| 2. |
- Persson, Kajsa P., et al.
(författare)
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Evaluation of Human Liver Slices and Reporter Gene Assays as Systems for Predicting the Cytochrome P450 Induction Potential of Drugs in Vivo in Humans
- 2006
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Ingår i: Pharmaceutical research. - New York : Springer. - 0724-8741 .- 1573-904X. ; 23:1, s. 56-69
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Tidskriftsartikel (refereegranskat)abstract
- PurposeThe aim of the study was to investigate the feasibility of predicting human in vivo cytochrome P450 (CYP) induction properties of drugs using in vitro methods.MethodsThe CYP induction potential of compounds was tested in human liver slices and in reporter gene assays for the aryl hydrocarbon receptor (AhR) and the pregnane X receptor (PXR).ResultsIn human liver slices, CYP activities decreased dramatically over the experimental period, whereas mRNA levels could reliably be used to investigate CYP1A, 2C9, and 3A4 induction. However, the interindividual variations and demanding experimentation limit the use of liver slices in screening programs. Reporter gene assays are robust and reliable assays, amenable to high throughput screening. Several compounds activated AhR. The relevance of this activation, however, needs to be further investigated since there are no clear reports on drugs inducing CYP1A in vivo. The results from the PXR assay could be used to correctly classify compounds with known CYP3A induction properties when relating in vivo AUCtot to PXR EC50 values.ConclusionsLiver slices are a valuable model to study the regulation of a larger number of enzymes by single compounds. The PXR reporter gene assay could be used as a reliable screening method to predict CYP3A induction in vivo. © 2006 Springer Science + Business Media, Inc.
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