Search results for "Neuroglobin"
showing 10 items of 54 documents
Neuroglobin and cytoglobin:two new entries in the hemoglobin superfamily.
2004
Abstract: Neuroglobin (Ngb) and cytoglobin (Cygb) are two newly discovered intracellular members of the vertebrate hemoglobin (Hb) family. Ngb, predominantly expressed in nerve cells, is of ancient evolutionary origin and is homologous to nerve-globins of invertebrates. Cygb, present in many different tissues, shares common ancestry with myoglobin (Mb) and can be traced to early vertebrate evolution. Ngb and Cygb display the classical three-on-three -helical globin fold and are endowed with a hexa-coordinate heme Fe atom, in both their ferrous and ferric forms, having the heme distal HisE7 residue as the endogenous sixth ligand. Reversible intramolecular hexa- to penta-coordination of the h…
Cytoglobin is a respiratory protein in connective tissue and neurons, which is up-regulated by hypoxia.
2004
Cytoglobin is a recently discovered vertebrate globin distantly related to myoglobin, and its function is unknown. Here we present the first detailed analysis of the distribution and expression of cytoglobin. Northern and Western blotting experiments show the presence of cytoglobin mRNA and protein in a broad range of tissues. Quantitative PCR demonstrates an up-regulation of cytoglobin mRNA levels in rat heart and liver under hypoxic conditions (22 and 44 h of 9% oxygen). Immunofluorescence studies with three antibodies directed against different epitopes of the protein consistently show cytoglobin in connective tissue fibroblasts as well as in hepatic stellate cells. Cytoglobin is also pr…
Neuroglobins from the Zebrafish Danio rerio and the Pufferfish Tetraodon nigroviridis
2001
Neuroglobin is a recently discovered respiratory, porphyrin-containing protein that is expressed in the brain of mouse and man. Here we show that neuroglobin is also present in the teleost fish. Complete cDNA sequences are reported from the pufferfish Tetraodon nigroviridis and the zebrafish Danio rerio. In addition, the neuroglobin gene of T. nigroviridis was sequenced, demonstrating the conservation of the B12.2, E11.0 and G7.0 introns plus the presence of an additional intron in the 5' noncoding region. The fish neuroglobins each comprise 159 amino acids and are 84.3% identical. Phylogenetic analyses show a basal position of the neuroglobins within the metazoan globin tree. An enhanced a…
Divergent Distribution in Vascular and Avascular Mammalian Retinae Links Neuroglobin to Cellular Respiration
2005
The visual function of the vertebrate retina relies on sufficient supply with oxygen. Neuroglobin is a respiratory protein thought to play an essential role in oxygen homeostasis of neuronal cells. For further understanding of its function, we compared the distribution of neuroglobin and mitochondria in both vascular and avascular mammalian retinae. In the vascular retinae of mouse and rat, oxygen is supplied by the outer choroidal, deep retinal, and inner capillaries. We show that in this type of retina, mitochondria are concentrated in the inner segments of photoreceptor cells, the outer and the inner plexiform layers, and the ganglion cell layer. These are the same regions in which oxyge…
Genomic Organization and Molecular Evolution of the Genes for Neuroglobin and Cytoglobin in the Hypoxiatolerant Israeli Mole Rat, Spalax Carmeli
2006
The genes for the two respiratory proteins neuroglobin (Ngb) and cytoglobin (Cygb) in the subterranean Israeli mole rat Spalax carmeli have been sequenced and compared to other mammals including human. Coding regions of both Spalax genes are highly conserved on the nucleotide and amino acid level. The ratios of non-synonymous to synonymous nucleotide substitutions suggest strong purifying selection acting on Ngb and Cygb in all mammals. Thus, there appears to be no special sequence level adaptation in the two respiratory proteins within the hypoxia-tolerant mole rat. On the genomic level, Spalax Ngb and Cygb gene regions revealed the conserved 4-exon-3-intron structure and conserved CpG-ric…
Oxygen Supply from the Bird's Eye Perspective
2011
The visual process in the vertebrate eye requires high amounts of metabolic energy and thus oxygen. Oxygen supply of the avian retina is a challenging task because birds have large eyes, thick retinae, and high metabolic rates but neither deep retinal nor superficial capillaries. Respiratory proteins such as myoglobin may enhance oxygen supply to certain tissues, and thus the mammalian retina harbors high amounts of neuroglobin. Globin E (GbE) was recently identified as an eye-specific globin of chicken (Gallus gallus). Orthologous GbE genes were found in zebra finch and turkey genomes but appear to be absent in non-avian vertebrate classes. Analyses of globin phylogeny and gene synteny sho…
Zebrafish Reveals Different and Conserved Features of Vertebrate Neuroglobin Gene Structure, Expression Pattern, and Ligand Binding
2004
Neuroglobin has been identified as a respiratory protein that is primarily expressed in the mammalian nervous system. Here we present the first detailed analysis of neuroglobin from a non-mammalian vertebrate, the zebrafish Danio rerio. The zebrafish neuroglobin gene reveals a mammalian-type exon-intron pattern in the coding region (B12.2, E11.0, and G7.0), plus an additional 5'-non-coding exon. Similar to the mammalian neuroglobin, the zebrafish protein displays a hexacoordinate deoxy-binding scheme. Flash photolysis kinetics show the competitive binding on the millisecond timescale of external ligands and the distal histidine, resulting in an oxygen affinity of 1 torr. Western blotting, i…
Ligation Tunes Protein Reactivity in an Ancient Haemoglobin: Kinetic Evidence for an Allosteric Mechanism in Methanosarcina acetivorans Protoglobin
2012
Abstract: Protoglobin from Methanosarcina acetivorans (MaPgb) is a dimeric globin with peculiar structural properties such as a completely buried haem and two orthogonal tunnels connecting the distal cavity to the solvent. CO binding to and dissociation from MaPgb occur through a biphasic kinetics. We show that the heterogenous kinetics arises from binding to (and dissociation from) two tertiary conformations in ligation-dependent equilibrium. Ligation favours the species with high binding rate (and low dissociation rate). The equilibrium is shifted towards the species with low binding (and high dissociation) rates for the unliganded molecules. A quantitative model is proposed to describe t…
Cyanide binding and heme cavity conformational transitions in **Drosophila melanogaster** hexacoordinate hemoglobin
2006
The reason for the presence of hemoglobin-like molecules in insects, such as Drosophila melanogaster, that live in fully aerobic environments has yet to be determined. Heme endogenous hexacoordination (where HisE7 and HisF8 axial ligands to the heme Fe atom are both provided by the protein) is a recently discovered mechanism proposed to modulate O-2 affinity in hemoglobins from different species. Previous results have shown that D. melanogaster hemoglobin 1 (product of the glob1 gene) displays heme endogenous hexacoordination in both the ferrous and ferric states. Here we present kinetic data characterizing the exogenous cyanide ligand binding process, and the three-dimensional structure (a…
The Heme Environment of Mouse Neuroglobin
2001
Neuroglobin (Ngb) is a newly discovered oxygen-binding heme protein that is primarily expressed in the brain of humans and other vertebrates. To characterize the structure/function relationships of this new heme protein, we have used resonance Raman spectroscopy to determine the structure of the heme environment in Ngb from mice. In the Fe2+CO complex, two conformations of the Fe–CO unit are present, one of which arises from an open conformation of the heme pocket in which the CO is not interacting with any nearby residue, and the other arises from a closed conformation where a positively charged residue near the CO group stabilizes the complex. For the Fe2+O2 complex, we detect a single νF…