76 research outputs found
Coupled Motions Direct Electrons along Human Microsomal P450 Chains
Directional electron transfer through biological redox chains can be achieved by coupling reaction chemistry to conformational changes in individual redox enzymes
How Does the Reductase Help To Regulate the Catalytic Cycle of Cytochrome P450 3A4 Using the Conserved Water Channel?
Characterization of Apoptosis-Related Oxidoreductases from Neurospora crassa
The genome from Neurospora crassa presented three open reading frames homologous to the genes coding for human AIF and AMID proteins, which are flavoproteins with oxidoreductase activities implicated in caspase-independent apoptosis. To investigate the role of these proteins, namely within the mitochondrial respiratory chain, we studied their cellular localization and characterized the respective null mutant strains. Efficiency of the respiratory chain was analyzed by oxygen consumption studies and supramolecular organization of the OXPHOS system was assessed through BN-PAGE analysis in the respective null mutant strains. The results demonstrate that, unlike in mammalian systems, disruption of AIF in Neurospora does not affect either complex I assembly or function. Furthermore, the mitochondrial respiratory chain complexes of the mutant strains display a similar supramolecular organization to that observed in the wild type strain. Further characterization revealed that N. crassa AIF appears localized to both the mitochondria and the cytoplasm, whereas AMID was found exclusively in the cytoplasm. AMID2 was detected in both mitochondria and cytoplasm of the amid mutant strain, but was barely discernible in wild type extracts, suggesting overlapping functions for the two proteins
Arginines 65 and 310 in Putidaredoxin Reductase Are Critical for Interaction with Putidaredoxin
Pyridine-Substituted Desoxyritonavir Is a More Potent Inhibitor of Cytochrome P450 3A4 than Ritonavir
Utilization of the cytochrome P450 3A4 (CYP3A4) inhibitor ritonavir as a pharmacoenhancer for anti-HIV drugs revolutionized the treatment of HIV infection. However, owing to ritonavir-related complications, there is a need for development of new CYP3A4 inhibitors with improved pharmacochemical properties, which requires a full understanding of the CYP3A4 inactivation mechanisms and the unraveling of possible inhibitor binding modes. We investigated the mechanism of CYP3A4 interaction with three desoxyritonavir analogues, containing the heme-ligating imidazole, oxazole, or pyridine group instead of the thiazole moiety (compounds 1, 2, and 3, respectively). Our data show that compound 3 is superior to ritonavir in terms of binding affinity and inhibitory potency owing to greater flexibility and the ability to adopt a conformation that minimizes steric clashing and optimizes protein–ligand interactions. Additionally, Ser119 was identified as a key residue assisting binding of ritonavir-like inhibitors, which emphasizes the importance of polar interactions in the CYP3A4–ligand association
Severe X-linked mitochondrial encephalomyopathy associated with a mutation in apoptosis-inducing factor.
We investigated two male infant patients who were given a diagnosis of progressive mitochondrial encephalomyopathy on the basis of
clinical, biochemical, and morphological features. These patients were born from monozygotic twin sisters and unrelated fathers, suggesting
an X-linked trait. Fibroblasts from both showed reduction of respiratory chain (RC) cIII and cIV, but not of cI activities.We found
a disease-segregating mutation in the X-linked AIFM1 gene, encoding the Apoptosis-Inducing Factor (AIF) mitochondrion-associated 1
precursor that deletes arginine 201 (R201 del). Under normal conditions, mature AIF is a FAD-dependent NADH oxidase of unknown
function and is targeted to the mitochondrial intermembrane space (this form is called AIFmit). Upon apoptogenic stimuli, a soluble
form (AIFsol) is released by proteolytic cleavage and migrates to the nucleus, where it induces ‘‘parthanatos,’’ i.e., caspase-independent
fragmentation of chromosomal DNA. In vitro, the AIFR201 del mutation decreases stability of both AIFmit and AIFsol and increases the
AIFsol DNA binding affinity, a prerequisite for nuclear apoptosis. In AIFR201 del fibroblasts, staurosporine-induced parthanatos was markedly
increased, whereas re-expression of AIFwt induced recovery of RC activities. Numerous TUNEL-positive, caspase 3-negative nuclei
were visualized in patient #1’s muscle, again indicating markedly increased parthanatos in the AIFR201 del critical tissues. We conclude
that AIFR201 del is an unstable mutant variant associated with increased parthanatos-linked cell death. Our data suggest a role for AIF in
RC integrity and mtDNA maintenance, at least in some tissues. Interestingly, riboflavin supplementation was associated with prolonged
improvement of patient #1’s neurological conditions, as well as correction of RC defects in mutant fibroblasts, suggesting that stabilization
of the FAD binding in AIFmit is beneficial
Exploration and evaluation of bioactive phytocompounds against BRCA proteins by in silico
Production and Characterization of a Functional Putidaredoxin Reductase−Putidaredoxin Covalent Complex
Uncovering the Role of Hydrophobic Residues in Cytochrome P450−Cytochrome P450 Reductase Interactions
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