A respiratory hemocyanin from an insect

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.

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“…However, spectroscopic properties and preliminary structural data indicate that G. intestinalis Hb is not a hexacoordinate Hb. 5 …”

Section: Discussionmentioning

confidence: 99%

“…A functional Hc has been identified so far only in the nymphs and adults of the stonefly Perla marginata (Plecoptera) (5). This Hc is composed of two distinct subunits and displays cooperative oxygen binding (n ϳ 2) with moderately oxygen affinity (P 50 ϳ 8 torr).…”

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

Journal of Biological Chemistry

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“…Insect hexamerins are part of a large family of hexameric proteins that are closely linked with diversifying evolution in arthropods (24). Strong evidence suggests that hexamerin-like proteins of terrestrial insects evolved from oxygen-carrying hemocyanins of ancestral aquatic insects and crustaceans (24,25). In terrestrial insects, the hexamerins have acquired diverse storage (26) and hormone-binding functions (19).…”

Section: Effects Of Rnai On Hexamerin Protein Expressionmentioning

confidence: 99%

Social exploitation of hexamerin: RNAi reveals a major caste-regulatory factor in termites

Zhou

Scharf

2006

Proc. Natl. Acad. Sci. U.S.A.

221

211

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Lower termites express a unique form of eusocial polyphenism in that totipotent workers can differentiate into either soldier or reproductive caste phenotypes. In this initial effort using RNA interference in termites, we found that two hexamerin genes, Hex-1 and Hex-2, participate in the regulation of caste polyphenism. Our methodology involved a dual gene-silencing approach that used a single short-interfering RNA fragment to silence the two homologous hexamerin genes. We performed validation studies that evaluated effects on nontarget housekeeping genes, silencing of a nonhousekeeping control gene, and effects at the protein level. We found that the two hexamerin proteins, which are inducible by the morphogenetic juvenile hormone and which constitute a significant proportion of total termite protein, suppress juvenile-hormone-dependent worker differentiation to the soldier caste phenotype. This mechanism allows termite colonies to retain high proportions of altruistic worker caste members, thus apparently enhancing colony-inclusive fitness. These findings demonstrate a unique status quo regulatory mechanism for termite worker caste retention and provide an example of previously undescribed preadult developmental͞caste-regulatory genes from any social insect.sociogenomics ͉ RNA interference ͉ short-interfering RNA ͉ juvenile hormone ͉ phenotypic plasticity

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“…Hemocyanins are copper-containing respiratory proteins, dissolved in concentrations up to 120 mg/ml in the hemolymph of molluscs and arthropods, including Crustacea, Chelicerata, Myriapoda, and some species of insects (Hagner-Holler et al 2004;Sánchez et al 1998;van Holde and Miller 1995;Chen et al 2007;Mičetic et al 2010). These molecules are composed of a number of subunits that assemble in an extremely large macro-molecular entity.…”

Section: Introductionmentioning

confidence: 99%

Structure and Characterization of Eriphia verrucosa Hemocyanin

et al. 2015

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Arthropod hemocyanins (Hcs) are a family of large extracellular oxygen-transporting proteins with high molecular mass and hexameric or multi-hexameric molecular assembly. This study reports for the first time the isolation and characterization of the structure of an arthropod hemocyanin from crab Eriphia verrucosa (EvH) living in the Black Sea. Its oligomeric quaternary structure is based on different arrangements of a basic 6 × 75 kDa hexameric unit, and four of them (EvH1, EvH2, EvH3, and EvH4) were identified using ion-exchange chromatography. Subunit 3 (EvH3) shows high similarity scores (75.0, 87.5, 91.7, and 75.0 %, respectively) by comparison of the N-terminal sequence of subunit 1 from Cancer pagurus of the North Sea (Cp1), subunits 3 and 6 of Cancer magister (Cm3 and Cm6), and subunit 2 of Carcinus aestuarii (CaSS2), respectively. Moreover, a partial cDNA sequence (1309 bp) of E. verrucosa hemocyanin encoding a protein of 435 amino acids was isolated. The deduced amino acid sequence shows a high degree of similarity with subunits 3, 4, 5, and 6 of C. magister (81-84 %). Most of the hemocyanins are glycosylated, and three putative O-linkage sites were identified in the partial amino acid sequence of EvH at positions 444-446, 478-480, and 547-549, respectively. The higher stability of native Hc in comparison to its subunit EvH4 as determined by circular dichroism (CD) could be explained with the formation of a stabilizing quaternary structure.

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A respiratory hemocyanin from an insect

Cited by 110 publications

References 25 publications

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

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

Social exploitation of hexamerin: RNAi reveals a major caste-regulatory factor in termites

Structure and Characterization of Eriphia verrucosa Hemocyanin

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