H Decker

..Therefore no new arrangement of the active site, with its two copper atoms and the mu - eta2:eta2 bound O2 molecule, is necessary to develop the catalytic function...

..The chelicerate hemocyanin subunits showing phenoloxidase activity may have evolved into a separate phenoloxidase in crustaceans...

..The oxygen binding behaviour of di-hexameric hemocyanins from cold and warm adapted animals do not show differences with respect to affinity, Bohr effect and cooperativity...

..Recent results reveal that haemocyanin also exhibits phenoloxidase activity. A scenario is proposed for the evolutionary relationships among copper oxygen-binding proteins (COPs)...

..We propose a peracarid-type hemocyanin that may have evolved in response to its required multiple functions in respiration and immune response, while phenoloxidase sensu strictu is lacking...

..This demonstrates that substrate specificity is not caused by a chemical modification of the active site...

..Possible advantages of a hierarchical cooperative model compared to a linear extension of the MWC model are discussed...

..However, our results demonstrate that, in contrast to the accepted paradigm, certain basal insects have retained an ancestral blood-based mechanism of gas exchange...

..In this way, different copper valencies are laterally distinguished under in vivo-like conditions, attributed to Cu(I) in the deoxy-state and Cu(II) in the oxy-state...

..We propose this might contribute to their allergic potential as well as their extreme stability with respect to temperature...

..The hexameric nature of arthropod tyrosinases suggests that these proteins were the ideal predecessors from which to develop the oxygen-carrier protein haemocyanin, with its allosteric and co-operative properties, later on...

..Upon oxygenation, KLH1 becomes smaller and more compact. Model reconstruction of KLH1 indicates a hollow cylinder with two rings located close to both ends, which move slightly together upon oxygenation...

..Cockroach allergens play a very important role in allergic diseases, especially asthma. The major allergen of the American cockroach (Periplaneta americana), Per a 3, naturally occurs as isoforms of hexamers...

..leptodactylus. The two binding sites differ strongly in their specificity towards the two analogues. It can be hypothesized that two different subunit types (beta and gamma) are responsible for the two types of binding sites...

..These observations lead to the hypothesis that a secondary, allosteric binding site exists, which binds dopamine and PTU and reduces the catalytic activity...

..In addition, another novel application is provided by these labels, i.e., the investigation of the influence of effectors by recording simultaneously the binding of oxygen in the visible and of effectors in the UV...

..Based on the agreement between oxygen binding curves and fluorescence titration we concluded that Prodan monitors a conformational transition of the allosteric unit...

..This study is a step in resolving conformational heterogeneities, involved in oxygen binding of hemocyanins, at the single-molecule level by AFM...

..Minor conformational differences at the active site seem to decide about whether the active site is only able to oxidize diphenols as in catecholoxidase or if it is also able to o-hydroxylate monophenols as in tyrosinase...

..Therefore, our model explains the mechanistic necessity for conservation of not only active site histidines but also adjacent amino acids in tyrosinase...

..We propose that the cupredoxin-like domain in both haemocyanin types once served to upload copper to the active site of the oxygen-binding domain...

..This structure reveals details of the monomeric conformation of the alpha-hemolysin, for example inherent flexibility, along with definite differences in comparison to the structures used as templates...

..It can be used as a model-free signal to investigate oxygen binding of hemocyanins at all aggregation levels. Furthermore it may provide a new way to analyse oxygen binding of phenoloxidases...

..This indicates that the activated hemocyanin behaves as a normal phenoloxidase...

..This review summarizes the present knowledge of bacterial tyrosinases, which are promising models in order to get more insights in structure, enzymatic reactions and functions of "type 3 copper" proteins in general...

..The dye's fluorescence is quenched due to Förster energy transfer to the oxygenated active sites of hemocyanin...

..This results explain for the first time, on a molecular basis, why fluorescence quantum yield can be used as an intrinsic signal for oxygen load of at least one arthropod hemocyanin, in particular that from the tarantula...

..Treatment with SDS of these hemocyanins results in an opening of the entrance to the active site for bulky phenolic compounds. This demonstrates, that almost all hemocyanin subunits possess the ability of catecholoxidase activity...

..Upon oxygenation, the KLH1 molecule becomes longer and skinnier. This study provides the first real evidence how a molluscan hemocyanin changes conformation during an allosteric transition...

..Thus, besides hemocyanins and GroEL, the hexagonal bilayer hemoglobins represent another class of proteins in which the hierarchical quaternary structure provides the basis for nested interaction in their functional properties...

..Thus both proteins might belong to a new class of haemolymph proteins present in the haemolymph of marine gastropods...

..Furthermore, the model also includes the existence of a conformation with very high ATPase activity. Such a conformation might be of importance at a certain stage in the folding cycle...

..It also shows a concept of allosteric interaction in hierarchically assembled proteins to guarantee the involvement of all subunits of a native oligomer to establish very high Hill coefficients...

..The results corroborate the presence of hierarchically organized interactions in this hemocyanin...

..Although the resolution was low, the hexamers and topological arrangement within the oligomers can be seen. However, the relative humidity seems to affect the height profiles...

..The amino acid exchange itself most probably has no impact on the three-dimensional structure of the receptor domain, suggesting that the phenotype is the result of altered receptor glycosylation and its pathophysiological consequences...

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..Features include rigid body modelling to result in static structures and three-dimensional probability densities using two different algorithms...

..vulgaris only during hypoxic conditions, i.e., either during environmental oxygen limitation or extensive exercise...

..The principle of membrane targeting in the absence of any genuine, high affinity receptor may also underlie the assembly of other lipid-inserted oligomers including cytotoxic peptides, protein toxins, and immune effector molecules...

..Under hypoxic conditions, the hexamers are expected not to be completely loaded with oxygen. Here, the dodecamers are supposed to be responsible for the oxygen supply...

..A similar phosphorylation-induced conformational change of the N-terminal domain has been observed by others in bovine annexin IV which, due to the conformational switch, also loses its membrane-aggregating property...

..The results showed that PNAE is a novel member of the alpha/beta hydrolase enzyme superfamily...

..It turned out to be much more complex than hitherto proposed: it displays D4 symmetry with a diameter of approximately 12 nm and a height of about 8 nm...

..californicum hemocyanin in solution...

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