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The structural basis that define the physiological functions of binuclear copper enzymes is discussed in the frame of the data generated by a broad spectroscopic approach, spanning from paramagnetic NMR and pulsed EPR to x-ray absorption spectroscopies. The structural features discussed for the different oxidation and ligation states accessible to a binuclear copper sites are the coordination geometry...
Time-resolved crystallography is a powerful technique that allows structural transitions to be followed in real time during the course of a chemical reaction. The extension of the time resolution of this technique to nanosecond and picosecond time scales require a short laser pulse to initiate the transition and a rapid polychromatic X-ray pulse to probe the structural perturbations. Unfortunately,...
Procedures are presented for the purification of the subunit dimer from Acanthochiton fasicularis hemocyanin. Electron microscopy of negatively stained specimens revealed a uniform population of macromolecules possessing the characteristic ''boat shape''. A 3D reconstruction from this EM data generated a ~3 nm resolution model that correlates well with earlier data of the purported subunit dimer,...
Tyrosinase was found to be active in the sulfoxidation of thioanisol, producing the (R)-sulfoxide with high enantiomeric excess. The activity of the enzyme with phenolic and diphenolic substrates in a mixed aqueous Hepes buffer pH 6.8-methanol-glycerol solvent was also investigated over a range of temperatures. These experiments enabled us to deduce the thermodynamic parameters associated with substrate...
Oxygen binding curves of single molecules promise to discriminate between different models describing cooperativity because load distributions are accessible. Individual tarantula hemocyanins could be detected by fluorescence correlation spectroscopy using intrinsic tryptophan fluorescence as sensor of bound oxygen. However, imaging of immobilized proteins was not possible due to fast photo-bleaching...
Sponges live in a symbiotic relationship with microorganisms, especially bacteria. Here we show, using the demosponge Suberites domuncula as a model, that the sponge expresses the enzyme tyrosinase which synthesizes diphenols from monophenolic compounds. It is assumed that these products serve as carbon source for symbiotic bacteria to grow.
Keyhole limpet hemocyanin (KLH) is known to share carbohydrate epitopes with Schistosoma mansoni. In order to define the structural basis for the observed serological cross-reactivity, KLH glycans were released either by enzyme treatment or by hydrazinolysis and probed with a rabbit hyperimmune serum directed against S. mansoni egg antigen. Both major, non-reacting oligosaccharide species as well...
Neuroglobin, mainly expressed in vertebrate brain and retina, is a recently identified member of the globin superfamily. Augmenting O 2 supply, neuroglobin promotes survival of neurons upon hypoxic injury, potentially limiting brain damage. In the absence of exogenous ligands, neuroglobin displays a six-coordinated heme. O 2 and CO bind to the heme-iron, displacing the endogenous HisE7...
Glycopeptides were isolated from functional units of two molluscan hemocyanins (Hcs). They were analyzed and localized in the sequences. A comparison with potential N-glycosylation sites of two other molluscan Hcs was made. An immunological cross-reactivity was observed between the beta-Hc and the alpha-macroglobulin of Helix pomotia. ELISA experiments with glycopeptide fractions indicated a competition.
A critical examination of the published molecular mass of erythrocruorin (Ec) from Lumbricus and related earthworm species reveals that the results do cluster, not at one, but at two values of the molecular mass. One cluster corresponds to ~3.6 MDa as predicted from the Vinogradov model for the hexagonal bilayer (HBL) assembly of Lumbricus terrestris EC and as estimated from the crystal structure...
The truncated hemoglobins from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 ligate the heme iron with two axial histidines (HisF8 and HisE10). In addition, these two proteins are able to form a heme-protein cross-link between a vinyl substituent and a histidine at position 16 of the H helix. The product is a protein with improved resistance to thermal and acid denaturation.
Laccases (EC 1.10.3.2, p-diphenol: dioxygen oxidoreductases) are multi-copper proteins that use molecular oxygen to oxidize various aromatic and non-aromatic compounds by a radical-catalyzed reaction mechanism. The enzymes are involved in the pathogenicity, immunity and morphogenesis of organisms and in the metabolic turnover of complex organic substances such as lignin or humic matter. Owing to their...
The quaternary structure of Molluscan hemocyanins is not still defined, in particular the spatial distribution and the structural subunits. It is important to establish the number and the nature of interations between functional units. Here we present two non-proteolytic methods for the depolymerization of hemocyanins. The results suggest that the carbohydrate moieties apparently play a basic role...
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