1,721,024 research outputs found
Anion-linked polymerization of the tetrameric hemoglobin from Scapharca inaequivalvis. Characterization and functional relevance.
No full textThe dimeric assembly of Photobacterium leiognathi and Salmonella typhimurium SodC1 Cu,Zn superoxide dismutases is affected differently by active site demetallation and pH: An analytical ultracentrifuge study
No full textTo establish whether the species-specific variations at the subunit interface of bacterial Cu,Zn superoxide dismutases affect dimer assembly, the association state of the Photobacterium leiognathi (PISOD) and Salmonella typhimurium (StSOD) enzymes, which differ in 11 out of 19 interface residues, was investigated by analytical ultracentrifugation. The same linkage pattern correlates quaternary assembly, active site metallation, and pH in the two enzymes albeit with quantitative differences. Both holo-enzymes are stable dimers at pH 6.8 and 8.0, although their shape is altered at alkaline pH. In contrast, dimer stability is affected differently by metal removal. Thus, apo-StSOD is a stable dimer at pH 6.8 whereas apo-PISOD is in reversible monomer-dimer equilibrium. In both apoproteins a pH increase to 8.0 favors monomerization. These effects prove the existence of long-range communication between the active site and the subunit interface and provide a structural explanation for the known functional differences between the two enzymes. (c) 2007 Elsevier Inc. All rights reserved
Identification of the site of ferrocyanide binding involved in the intramolecular electron transfer process to oxidized heme in Scapharca dimeric hemoglobin.
No full textThe neutrophil-activating Dps protein of Helicobacter pylori, HP-NAP, adopts a mechanism different from Escherichia coli Dps to bind and condense DNA
No full textA novel mechanism of heme-heme interaction in the homodimeric hemoglobin from Scapharca inaequivalvis as manifested upon cleavage of the proximal Fe-N epsilon bond at low pH.
No full textThe CO-binding kinetics and the optical spectra of the NO derivative of the homodimeric hemoglobin from Scapharca inaequivalvis have been investigated over the range between pH 7.0 and 2.0. In the deoxygenated derivative, protonation of the proximal imidazole at very low pH values and the consequent cleavage of the Fe-N epsilon bond result in a approximately 50-fold enhancement of the rate constant for CO binding, as found in other hemoproteins. However, in the case of the hemoglobin from S. inaequivalvis, the pH profile displays a cooperative behavior (n = 1.8 +/- 0.1), a unique feature that differentiates this protein from any other hemoprotein investigated thus far. Cleavage of the proximal bond in the NO derivative of S. inaequivalvis hemoglobin likewise displays a very steep pH transition. The mode of assembly of the homodimer, in which the heme-carrying E and F helices provide the subunit interface and bring the hemes at a much shorter distance (18.4 A) than in vertebrate hemoglobins, is likely to provide the structural basis for this unique behavior
A novel mechanism of heme-heme interaction in the homodimeric hemoglobin from Scapharca inaequivalvis as manifested upon cleavage of the proximal Fe-N epsilon bond at low pH
No full textStructural characterization of oxidized dimeric Scapharca inaequivalvis hemoglobin by resonance Raman spectroscopy.
No full textDps proteins prevent Fenton-mediated oxidative damage by trapping hydroxyl radicals within the protein shell
No full textDps (DNA-binding proteins from starved cells) proteins belong to a widespread bacterial family of proteins expressed under nutritional and oxidative stress conditions. In particular, Dps proteins protect DNA against Fenton-mediated oxidative stress, as they catalyze iron oxidation by hydrogen peroxide at highly conserved ferroxidase centers and thus reduce significantly hydroxyl radical production. This work investigates the possible generation of intraprotein radicals during the ferroxidation reaction by Escherichia coli and Listeria innocua Dps, two representative members of the family. Stopped-flow analyses show that the conserved tryptophan and tyrosine residues located near the metal binding/oxidation center are in a radical form after iron oxidation by hydrogen peroxide. DNA protection assays indicate that the presence of both residues is necessary to limit release of hydroxyl radicals in solution and the consequent oxidative damage to DNA. In general terms, the demonstration that conserved protein residues act as a trap that dissipates free electrons generated during the oxidative process brings out a novel role for the Dps protein cage. © 2009 Elsevier Inc. All rights reserved
Effect of inositol hexakisphosphate on the EPR properties of the nitric oxide derivative of ferrous dromedary (Camelus dromedarius) hemoglobin. Evidence for two polyanion binding sites
No full textHeme-heme interactions in a homodimeric cooperative hemoglobin. Evidence from transient Raman scattering.
No full text- …
