T Burmester

..Neuroglobin represents a distinct protein family that diverged early in metazoan evolution, probably before the Protostomia/Deuterostomia split...

..The time of divergence of the insect proteins from the malacostracan hemocyanins was estimated to be about 430-440 MYA, providing support for the notion that the Hexapoda evolved from the same crustacean lineage as the Malacostraca...

..This indicates that the vertebrate myoglobins are in fact a specialized intracellular globin that evolved in adaptation to the special needs of muscle cells...

..Neuroglobin appears to be associated with mitochondria-rich cell types and thus oxygen consumption rates, suggesting a myoglobin-like function of this protein in facilitated oxygen diffusion...

..Database and gene synteny analyses confirm the absence of a myoglobin gene in X. tropicalis...

..Hence, haemocyanin-related storage proteins emerged at least two times independently in Hexapoda...

..The latter topology is also supported by a unique shared deletion of an alpha-helix. A common ancestry of Myriapoda and Chelicerata should be seriously considered...

..The cytoglobin gene, in contrast, harbors both conserved HREs and mRNA stabilization sites, strongly suggestive of an oxygen-dependent regulation...

..Under the assumption of a molecular clock we calculated that alpha- and gamma-subunits split about 214 +/- 14 million years ago, suggesting their divergence only in the decapod Crustacea...

..93 x 10(-9) amino acid substitutions per site and year) compared with their mammalian proteins ( approximately 0.39 x 10(-9) replacements per site and year)...

..Surprisingly, cytoglobin is localized in both the cytoplasm and nucleus of neurons, indicating a possible additional role of this protein in neuronal tissues...

..Molecular clock calculations using hexamerins suggest that the divergence of Zygentoma and Pterygota occurred around 387 million years ago, which is in excellent agreement with the available fossil record...

..The hemocyanins evolved in agreement with the expected phylogeny of the Arthropoda, with the Onychophora diverged first, followed by the Chelicerata and Pancrustacea. The position of the myriapod hemocyanins is not resolved...

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..The molecular model shows the amino acid residues involved, and reveals that several of the interfaces are intriguingly histidine-rich and likely to transfer allosteric signals between the different levels of the nested hierarchy...

..0. Phylogenetic analyses suggest that this globin is most closely related to the cytoglobin lineage. Although the function of this eye-globin remains presently uncertain, it adds an additional diversity to the vertebrate globin family...

..Our results clearly demonstrate an association of neuroglobin and mitochondria, thus supporting the hypothesis that neuroglobin is a respiratory protein that supplies oxygen to the respiratory chain...

..Phylogenetic analyses do not support a common clade of Myriapoda and Hexapoda, whereas there is evidence in favor of monophyletic Mandibulata...

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..However, Cygb-2 is more than 250-fold stronger expressed in neuronal tissues, suggesting a subfunctionalization of the two cytoglobin paralogs after gene duplication...

..Phylogenetic analyses confirm an ancient evolutionary relationship of globin X with neuroglobin and suggest the existence of two distinct globin types in the last common ancestor of Protostomia and Deuterostomia...

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..While neuroglobin seems to be associated with oxygen consumption, a respiratory function of cytoglobin is unlikely...

..Sequence comparison shows that the hexamerins and hexamerin receptors diverged early in insect evolution and derive from a common hemocyanin ancestor...

..glob1 is closely related to the intracellular hemoglobin of the botfly Gasterophilus intestinalis, and the extracellular hemoglobins from the chironomid midges derive from this clade...

..Cytoglobin is also expressed in distinct cell types of brain and retina. Its distribution strikingly differs from neuroglobin, suggesting an independent, yet unknown function...

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..This suggests that oxygen supply in insects may be more complex than thought previously and may depend on hemoglobin-mediated oxygen transport and storage in addition to simple diffusion...

..For example, LAST_MAM is the only astacin protease known so far that is active in its zymogen form, indicating that the presence of the N-terminal propeptide does not prevent proteolytic activity...

..Nevertheless, the occurrence of respiratory proteins in insects adds further complexity to our view on insect respiration...

..Assuming a clock-like evolution of the chelicerate hemocyanins, a timescale for the evolution of the Chelicerata was obtained that agrees with the fossil record...

..6 kDa). Phylogenetic analyses of the arthropod hemocyanin sequences show that the Onychophora form a robust sister-group of the Euarthropoda, whereas the monophyly of the Tracheata is not supported...

..Hemocyanins also gave rise to non-respiratory proteins (crustacean pseudo-hemocyanins, insect hexamerins, and hexamerin receptors), which most likely have storage functions...

..By molecular modelling, we have found the putative locations for the amino acid sequence (597-605) and the C-terminal end (654-657), which are absent in the available P.interruptus X-ray data...

..This result suggests either multiple independent functional changes or a yet undefined respiratory role of tissue globins like Ngb and Cygb...

..Molecular phylogenetic analyses show a close relationship of the crustacean and insect proteins, providing strong support for a pancrustacean taxon, while structural data suggest a myriapod-chelicerate clade...

..Cytoglobin is predominantly expressed in fibroblasts and related cell types, but also in distinct nerve cell populations. Much less is known about its function, although in fibroblasts it might be involved in collagen synthesis...

..Rather, dmeglob1 may protect the fly from an excess of O2, either by buffering the flux of O2 from the tracheoles to the cells or by degrading noxious reactive oxygen species...

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..These findings suggest that neuroglobin supplies oxygen to the retina, similar to myoglobin in the myocardium and the skeletal muscle...

..Analysis of the neuroglobin genomic sequence from man and mouse identifies sequence motifs with similarity to the neuron-restrictive silencer element, possibly explaining a neuron-specific expression of neuroglobin...

..There was little change in the expression of the two cytoglobin genes. Globin X mRNA significantly decreased under hypoxia, pointing to a functional linkage to oxygen-dependent metabolism...

..Although insect hemoglobins may be in fact involved in oxygen metabolism, it remains uncertain whether they carry out a myoglobin-like function in oxygen storage and delivery...

..0, providing evidence for a recent intron gain event. Both mosquito glob2 genes have lost the B12.2 intron. This pattern must be interpreted in terms of dynamic intron gain and loss events in the globin gene lineage...

..Regionally differing intensities of immunostaining suggest different levels of neuroglobin protein expression, in line with the idea that brain regions show variation in their tolerance towards hypoxic conditions...

..Delayed gene expression response is characterised by inflammation and immune-related genes. These results support the hypothesis that the brain's response to ischemia is an active, specific and coordinated process...

..This effect could be of biological relevance for certain organisms, since it could provide a globin with an oxygen affinity that is nearly independent of temperature...

..This effect could be of biological relevance for certain organisms, since it would lead to an oxygen affinity that is nearly independent of temperature...

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..Therefore, it is unlikely that neuroglobin is instrumental in the acute response of neurons to hypoxic or ischemic insults, for which the mammalian brain is not adapted...

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..Cell culture data suggest that in fibroblasts Cygb is involved in cell proliferation, possibly in collagen synthesis. In neurons, there is evidence for an additional role of Cygb related to nitric oxide metabolism...

..In agreement with previous studies, we have demonstrated that random sequencing of cDNAs results in sequence information suitable for phylogenomic approaches to resolve metazoan relationships...

..95 A resolution using synchrotron radiation. The crystals belong to space group P2(1), with unit-cell parameters a = 39.6, b = 94.9, c = 67.5 A, beta = 94.4 degrees, and contain 2-4 protein molecules per asymmetric unit...

..These results demonstrate a remarkable diversity in oxygenation characteristics of vertebrate and invertebrate nerve haemoglobins that clearly reflect distinct physiological roles...

..Strikingly, the data reveal that O2 metabolism in cells is more complicated than was thought before, requiring unexpected O2-binding proteins with potentially novel functional features...

..Despite the conserved globin fold, the cavity found in CYGB* is structured differently from those recognized to play a functional role in myoglobin, neuroglobin, truncated hemoglobins, and Cerebratulus lacteus mini-hemoglobin...

..The cavity, which may provide a heme ligand diffusion pathway, is connected to the external space through a narrow tunnel nestled between the globin G and H helices...

..Neuroglobin may promote neuronal survival under hypoxic conditions as they occur, for example, in stroke...

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

..Hence the oxygen affinity would be directly linked to the redox state of the cell...

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..This suggests a novel mechanism for the oxygen binding; reduction of the disulfide bond would provoke the release of oxygen...

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..Despite the high resolution achieved, no sequence/structure features specifically supporting the heme hexa- to pentacoordination transition required for diatomic ligand binding could be recognized...

..8, b = 73.1, c = 98.9 A and two molecules per asymmetric unit. The anomalous difference Patterson map clearly reveals the position of the haem Fe-atom sites, thus paving the way for SAD structure determination...

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..This finding is in agreement with the ancestral phylogeny of the vertebrate globins. Moreover, it seems likely that the Ciona hemocyanin-like sequences have enzymatic instead of respiratory functions...

..They most likely fulfill a myoglobin-like function and enhance oxygen supply to the neurons...

..These findings will facilitate the use of the zebrafish as a model organism in the study of the physiological role of POMC-derived peptides...

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..Examples are shown based on globin sequences from various species and on the abnormal human hemoglobins. The software should be of interest to protein engineers who need to know what variants are already known...