Search results for "Cytochrome b Group"
showing 10 items of 13 documents
A spontaneous mitonuclear epistasis converging on Rieske Fe-S protein exacerbates complex III deficiency in mice
2020
We previously observed an unexpected fivefold (35 vs. 200 days) difference in the survival of respiratory chain complex III (CIII) deficient Bcs1lp.S78G mice between two congenic backgrounds. Here, we identify a spontaneous homoplasmic mtDNA variant (m.G14904A, mt-Cybp.D254N), affecting the CIII subunit cytochrome b (MT-CYB), in the background with short survival. We utilize maternal inheritance of mtDNA to confirm this as the causative variant and show that it further decreases the low CIII activity in Bcs1lp.S78G tissues to below survival threshold by 35 days of age. Molecular dynamics simulations predict D254N to restrict the flexibility of MT-CYB ef loop, potentially affecting RISP dyna…
Isolation and partial characterization of a cytochrome-o complex from chromatophores of the photosynthetic bacterium Rhodospirillum rubrum FR1.
1989
A cytochrome-o complex was isolated from chromatophores of photoheterotrophically grown Rhodospirillum rubrum FR1. The enzyme was extracted with the non-denaturating detergent taurodeoxycholate and subsequently purified by sucrose-density-gradient centrifugation and gel-permeation HPLC. The complex contains two types of cytochromes, one of them cytochrome o, and two copper atoms. It catalyzes the reduction of molecular oxygen, when N,N,N',N'-tetramethyl-p-phenylenediamine or ubiquinol 10 are offered as electron donors. The oxidase activity is inhibited by cyanide, carbon monoxide and 2-heptyl-2-hydroxyquinoline N-oxide. The molecular mass of the protein is 136 +/- 15 kDa. The subunit analys…
Phylogeography of the Eurasian Willow Tit (Parus montanus) based on DNA sequences of the mitochondrial cytochrome b gene.
2002
The phylogeographic relationships of the trans-Palearctic Willow Tit assemblage were studied by obtaining sequence data from the mitochondrial cytochrome b gene from 34 specimens representing nine subspecies from across the species range. Four distinct genetic groups were identified: Parus montanus weigoldicus, P. m. affinis, P. m. songarus, and a clade containing six Eurasian subspecies (ssp. baicalensis, borealis, montanus, restrictus, rhenanus, and sachalinensis). P. m. weigoldicus, P. m. affinis, and P. m. songarus were reciprocally monophyletic and separated from each other and other subspecies by uncorrected genetic distances between 1.9 and 5.8%. The remaining six subspecies were clo…
Influence of gallic acid esters on drug-metabolizing enzymes of rat liver
1982
The effect of three antioxidants, propyl, octyl and dodecyl gallate, on hepatic drug metabolism in male rats was studied in vivo and in vitro. When fed at a dietary concentration of 1% for 14 days, only dodecyl gallate increased relative liver weight. Cytochrome P-450 content was not influenced, but a slight increase in cytochrome b5 content was observed after the feeding of propyl gallate. Monooxygenase activity (benzo[a]pyrene-hydroxylase and ethoxycoumarin-deethylase activities) was not affected by propyl or octyl gallate, but a significant decrease in benzo[a]pyrene-hydroxylase activity was apparent in rats fed dodecyl gallate. Study of benzo[a]pyrene-metabolite formation in liver micro…
The mitochondrial genome of fission yeast: inability of all introns to splice autocatalytically, and construction and characterization of an intronle…
1991
In this paper we report the inability of four group I introns in the gene encoding subunit I of cytochrome c oxidase (cox1) and the group II intron in the apocytochrome b gene (cob) to splice autocatalytically. Furthermore we present the characterization of the first cox1 intron in the mutator strain anar-14 and the construction and characterization of strains with intronless mitochondrial genomes. We provide evidence that removal of introns at the DNA level (termed DNA splicing) is dependent on an active RNA maturase. Finally we demonstrate that the absence of introns does not abolish homologous mitochondrial recombination.
Phylogeny of the Drosophila obscura species group deduced from mitochondrial DNA sequences
1994
Approximately 2 kb corresponding to different regions of the mtDNA of 14 different species of the obscura group of Drosophila have been sequenced. In spite of the uncertainties arising in the phylogenetic reconstruction due to a restrictive selection toward a high mtDNA A+T content, all the phylogenetic analysis carried out clearly indicate that the obscura group is formed by, at least, four well-defined lineages that would have appeared as the consequence of a rapid phyletic radiation. Two of the lineages correspond to monophyletic subgroups (i.e., affinis and pseudoobscura), whereas the obscura subgroup remains heterogeneous assemblage that could be reasonably subdivided into at least two…
Heme Binding Constricts the Conformational Dynamics of the Cytochrome b559′ Heme Binding Cavity
2012
Cytochrome b(559)' is a transmembrane protein formed by homodimerization of the 44-residue PsbF polypeptide and noncovalent binding of a heme cofactor. The PsbF polypeptide can dimerize in the absence and presence of heme. To monitor structural alterations associated with binding of heme to the apo-cytochrome, we analyzed the apo- and holo-cytochrome structure by electron paramagnetic resonance spectroscopy. Spin labeling of amino acids located close to the heme binding domain of the cytochrome revealed that the structure of the heme binding domain is unconstrained in the absence of heme. Heme binding restricts the conformational dynamics of the heme binding domain, resulting in the structu…
A Ser residue influences the structure and stability of a Pro-kinked transmembrane helix dimer
2012
AbstractWhen localized adjacent to a Pro-kink, Thr and Ser residues can form hydrogen bonds between their polar hydroxyl group and a backbone carbonyl oxygen and thereby modulate the actual bending angle of a distorted transmembrane α-helix. We have used the homo-dimeric transmembrane cytochrome b559′ to analyze the potential role of a highly conserved Ser residue for assembly and stabilization of transmembrane proteins. Mutation of the conserved Ser residue to Ala resulted in altered heme binding properties and in increased stability of the holo-protein, most likely by tolerating subtle structural rearrangements upon heme binding. The results suggest a crucial impact of an intrahelical Ser…
Six amino acids define a minimal dimerization sequence and stabilize a transmembrane helix dimer by close packing and hydrogen bonding
2013
AbstractDistinct amino acid sequences have been described to mediate oligomerization of transmembrane α-helices. However, as the sequence context is crucial to determine specificity in transmembrane helix–helix interaction, the question arises how small a sequence can be without losing specificity. In the present analysis, six amino acids have been identified in the PsbF transmembrane helix dimer, which form the contact region of two interacting helices and are directly involved in helix–helix interactions. However, individual amino acids within the complex sequence pattern only together ensure sequence specificity of the analyzed transmembrane helix–helix interactions by mediating close pa…
Paraphyly of the Blue Tit (Parus caeruleus) suggested from cytochrome b sequences
2002
The phylogenetic relationships of the Blue Tit-Azure Tit assemblage (genus Parus; Aves: Passeriformes) were studied using mitochondrial DNA sequences of 24 specimens representing seven subspecies from Eurasia and North Africa. Previous work based on comparative morphological and acoustic data suggested a division of the Blue Tit (Parus caeruleus) into two species. Our analyses clearly indicate that the Blue Tit represents a paraphyletic assemblage, including a European/Middle Asian clade that is the sister group to the Azure Tit (Parus cyanus) and a North African clade. The North African clade (teneriffae subspecies group) is a sister group to the European Blue Tit/Azure Tit clade. We sugge…