Search results for "Heme B"
showing 10 items of 10 documents
Assembly of Transmembrane b-Type Cytochromes and Cytochrome Complexes
2016
Cytochromes are involved in charge-transfer reactions, and many cytochromes contain a transmembrane domain and are part of membrane-localized electron transfer chains. Protoporphyrin IX (heme b) is the first heme product in the tetrapyrrole/heme biosynthesis pathway. In contrast to c-type cytochromes, there is no need for a specialized machinery catalyzing covalent attachment of the heme molecule to a b-type apo-cytochrome, nor is the cofactor further modified, as in a-, d- and o-type cytochromes. Thus, formation of a holo-cytochrome is relatively simple for b-type cytochromes, and this class of proteins probably represents the most ancient members of transmembrane cytochromes. However, ass…
Fasciola spp: Mapping of the MF6 epitope and antigenic analysis of the MF6p/HDM family of heme-binding proteins
2017
MF6p/FhHDM-1 is a small cationic heme-binding protein which is recognized by the monoclonal antibody (mAb) MF6, and abundantly present in parenchymal cells and secreted antigens of Fasciola hepatica. Orthologs of this protein (MF6p/HDMs) also exist in other causal agents of important foodborne trematodiasis, such as Clonorchis sinensis, Opisthorchis viverrini and Paragonimus westermani. Considering that MF6p/FhHDM-1 is relevant for heme homeostasis in Fasciola and was reported to have immunomodulatory properties, this protein is expected to be a useful target for vaccination. Thus, in this study we mapped the epitope recognized by mAb MF6 and evaluated its antigenicity in sheep. The sequenc…
"Table 4" of "Measurement of matter-antimatter differences in beauty baryon decays"
2017
For $\Lambda_b^0\to p\pi^-\pi^+\pi^-$ decays, the CP- and P-violating observables, $a^{\hat{T}-odd}_{CP}$ and $a^{\hat{T}-odd}_{P}$, resulting from the fit to the data are listed with their statistical and systematic uncertainties. Each value is obtained through an independent fit to a region of the phase space defined in Scheme B.
"Table 2" of "Measurement of matter-antimatter differences in beauty baryon decays"
2017
Definition of binning scheme B for the decay mode $\Lambda_b^0\to p\pi^-\pi^+\pi^-$.
Solid-State Electrochemical Assay of Heme-Binding Molecules for Screening of Drugs with Antimalarial Potential
2013
The interaction between heme and ligands is the basis for a variety of tests aimed at the discovery of antiplasmodial molecules. Two electrochemical methods for the screening of molecules with potential antimalarial activity through heme-binding mechanism are described. The first method is applicable to lipophilic environment, by using solution phase electrochemistry in DMSO solutions of Fe(III)-heme plus the tested compounds at carbon electrodes. This method provides well-defined voltammetric signals, characteristic of the heme-ligand (L) interaction. The second method involves aqueous media at biological pH and the use of voltammetry of immobilized particles, by means of microparticulate …
Interaction of iron(II)-heme and artemisinin with a peptide mimic of Plasmodium falciparum HRP-II
2007
Abstract The interaction of heme or heme-artemisinin adducts (heme-art) with different peptides mimicking repeat sequences of the Histidine-Rich-Protein-II of Plasmodium falciparum (PfHRP-II) was investigated. The pseudo-first order rate constants of the coordination of heme or heme-art onto a histidine rich peptide, used as a mimic of PfHRP-II putative heme binding sequence, are of the same order of magnitude, namely 42 and 14 s −1 , respectively. Despite the intrinsic reactivity of the carbonyl at C10 of heme-art toward a hydroxyl function, a peptide containing a serine or threonine residue does not readily react with heme-art adducts. Therefore, a much higher affinity of heme-art compare…
A PAS domain with an oxygen labile [4Fe-4S](2+) cluster in the oxygen sensor kinase NreB of Staphylococcus carnosus.
2008
The cytoplasmic histidine sensor kinase NreB of Staphylococcus carnosus responds to O(2) and controls together with the response regulator NreC the expression of genes of nitrate/nitrite respiration. nreBC homologous genes were found in Staphylococcus strains and Bacillus clausii, and a modified form was found in some Lactobacillus strains. NreB contains a sensory domain with similarity to heme B binding PAS domains. Anaerobically prepared NreB of S. carnosus exhibited a (diamagnetic) [4Fe-4S](2+) cluster when assessed by Mossbauer spectroscopy. Upon reaction with air, the cluster was degraded with a half-life of approximately 2.5 min. No significant amounts of Mossbauer or EPR detectable i…
SDS-facilitated in vitro formation of a transmembrane B-type cytochrome is mediated by changes in local pH.
2011
Abstract The folding and stabilization of α-helical transmembrane proteins are still not well understood. Following cofactor binding to a membrane protein provides a convenient method to monitor the formation of appropriate native structures. We have analyzed the assembly and stability of the transmembrane cytochrome b 559 ′, which can be efficiently assembled in vitro from a heme-binding PsbF homo-dimer by combining free heme with the apo-cytochrome b 559 ′. Unfolding of the protein dissolved in the mild detergent dodecyl maltoside may be induced by addition of SDS, which at high concentrations leads to dimer dissociation. Surprisingly, absorption spectroscopy reveals that heme binding and…
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…