Structural, Functional, and Genetic Characterization of Gastrophilus Hemoglobin

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In contrast to previous assumptions, the fruit fly Drosophila melanogaster possesses hemoglobin. This respiratory protein forms a monomer of about 17 kDa that is not exported into the hemolymph. Recombinant Drosophila hemoglobin displays a typical hexacoordinated deoxy spectrum and binds oxygen with an affinity of 0.12 torr. Four different hemoglobin transcripts have been identified, which are generated by two distinct promoters of the hemoglobin (glob1) gene but are identical in their coding regions. Putative binding sites for hypoxia-regulated transcription factors have been identified in the gene. Hemoglobin synthesis in Drosophila is mainly associated with the tracheal system and the fat body. 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.

Section: Table I Ligand Binding Kinetics Of Drosophila Hb and Other Smentioning

confidence: 90%

Section: Table I Ligand Binding Kinetics Of Drosophila Hb and Other Smentioning

confidence: 99%

mentioning

confidence: 99%

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Characterization of DrosophilaHemoglobin

Hankeln

Jaenicke

Kiger

et al. 2002

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“…Hbs at high concentrations have been found in a few insects that live, at least temporarily, in a hypoxic environment, such as the aquatic larvae of chironomid midges (6), some aquatic backswimmers (7), and the larvae of the horse botfly Gasterophilus intestinalis (8). These species harbor single chain Hbs (ϳ150 amino acids) in millimolar concentrations which either transport oxygen in the hemolymph (midges) or store oxygen in specialized tissues (backswimmers and botfly) (3,9).…”

Section: Or Hemocyanins (Hcs) (2-4)mentioning

confidence: 99%

Bishistidyl Heme Hexacoordination, a Key Structural Property in Drosophila melanogaster Hemoglobin

Sanctis¹,

Dewilde

Vonrhein

et al. 2005

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Hemoglobins at high concentration have been isolated long ago from some insect larvae living in hypoxic environments. Conversely, a monomeric hemoglobin has been discovered recently in the fruit fly Drosophila melanogaster as intracellular protein expressed both in larvae and in the adult fly. Such a finding indicates that the oxygen supply in insects may be more complex than previously thought, relying not only on O 2 diffusion through the tubular tracheal system, but also on carriermediated transport and storage. We present here the crystal structure of recombinant D. melanogaster hemoglobin at 1.20 Å resolution. Spectroscopic data show that the protein displays a hexacoordinated heme, whose axial ligands are the proximal and distal His residues. Such bis-His ligation of the heme has sizable effects on the protein local structure. Three protein matrix cavities, comparable in size but not in topological locations with those of sperm whale myoglobin, are spread through the protein matrix; one of these can host a xenon atom. Additionally, D. melanogaster hemoglobin binds one molecule of 3-(cyclohexylamino)propanesulfonic acid (CAPS) buffer at a surface pocket, next to the EF hinge. 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.

“…There are three possible explanations for this heterogeneity: (i) the described variations (see below) suggest the presence of multiple copies of the same gene such that allelic as well as nonallelic variations can occur, (ii) post-translational modifications, or (iii) artificial modifications might be induced by the extraction and separation procedures used (21). It should be considered however that in invertebrates as well as in vertebrates, multiple copies of globin genes are a rule rather than an exception (33)(34)(35). Therefore this multiplicity could most likely be explained by the necessity to synthesize huge amounts of the oxygen carrier (35).…”

Section: In L Terrestris)mentioning

confidence: 99%

The Primary Structure of Globin and Linker Chains from the Chlorocruorin of the Polychaete Sabella spallanzanii

Pallavicini¹,

Negrisolo²,

Barbato³

et al. 2001

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Annelid hemoglobins are organized in a very complex supramolecular network of interacting polypeptides, the structure of which is still not wholly resolved. We have separated by two-dimensional electrophoresis the 4-MDa chlorocruorin of Sabella spallanzanii and identified its components by amino-terminal sequencing. This work reveals a high rate of heterogeneity of constituent chains in a single animal as well as in the Sabella population. Using a cDNA library prepared from the hematopoietic tissue of this worm, we have isolated and fully sequenced most globin and linker cDNAs. The primary structure features of these polypeptides have been characterized by comparison with model globin and linker sequences.