Hemocyanin—a current perspective

Ellerton, H. David; Ellerton, Nerida F.; Robinson, Heather

doi:10.1016/0079-6107(83)90028-7

Cited by 168 publications

(75 citation statements)

References 394 publications

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“…Comparative studies on the association state of these Hcs revealed a main component with 39S sedimentation coefficient, which corresponds to the 4 × 6-mer of chelicerates (Roxby et al, 1974;Miller and van Holde, 1974;Miller et al, 1977;Ellerton et al, 1983;Miller and van Holde, 1982;Taylor et al, 2000). In addition, a minor pool of Hc in the 1 × 6-meric form (17S) was described.…”

Section: Introductionmentioning

confidence: 97%

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

Paoli

Giomi

Hellmann³

et al. 2007

Gene

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Section: Introductionmentioning

confidence: 97%

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

Paoli

Giomi

Hellmann³

et al. 2007

Gene

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“…The 16S unit is a hexamer of 5S functional subunits. The specific aggregation forms, present in the hemolymph of the various animals, depend on the species (van Holde and van Bruggen, 1971;Markl, 1986;Ellerton et al, 1983). In the hemolymph of most crustacea, hexamers (16S) or dodecamers (24S) or both are found.…”

mentioning

confidence: 99%

“…However, the biological significance for the occurrence of such different aggregation forms is still controversial (Markl and Decker, 1992). Dissociation in functionally intact subunits can be accomplished by removing Ca 2ϩ and increasing the pH above 9.0 (Ellerton et al, 1983; van Holde and Miller, 1995). Various studies elucidate the subunit composition of crustacean Hc.…”

mentioning

confidence: 99%

Subunits composition and allosteric control in Carcinus aestuarii hemocyanin

Dainese

Muro

Beltramini

et al. 1998

European Journal of Biochemistry

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Carcinus aestuarii hemocyanin (Hc) exists in two aggregation forms at pH 7.5 and 20 mM Ca 2ϩ : 24S accounting for 90% of total hemocyanin and 16S accounting for 10%. Removal of metal cations by EDTA at neutral pH causes the complete dissociation of 24S hemocyanin into two different 16S. At pH 9.2, 24S hemocyanin dissociates into a pH stable 16S and a 5S component. The 5S component consists of three monomeric fractions named CaeSS1 (10%), CaeSS2 (50%) and CaeSS3 (40%); the latter fraction consisting of two isoforms. The fractions CaeSS1, CaeSS2 and CaeSS3 have been studied as far as their reassociation properties to form hexamers are concerned. We investigated the oxygen-binding properties of the native form (24S), the mixture of the two 16S forms, the pH-stable 16S alone and of purified subunit fractions to define the role of each species on the expression of the allosteric behaviour of the 24S aggregate. The analysis of O 2 -binding data reveals that 24S-Hc can be well described by the modified Monod Wyman and Changeaux-model (nested MWC-model), while the half-molecules (16S) bind oxygen according to the simple MWC-model. The two hexameric 16S within the dodecameric 24S hemocyanin can be regarded as nested allosteric units. They behave as being functionally coupled in the T-states (tT and rT). In the R-states (tR and rR) the two half-molecules seem to be functionally uncoupled since they have the same values of oxygen binding constants as deduced for isolated 16S hexamers.Keywords : hemocyanin; subunit; heterogeneity; oxygen binding ; allostery ; nesting.Hemocyanins (Hc) are giant oligomeric copper-containing proteins. They occur freely dissolved in the hemolymph and are responsible for oxygen transport in many arthropods and molluscs (Ghiretti, 1962;Préaux and Gielens, 1984;Salvato and Beltramini, 1990; van Holde and Miller, 1995). Arthropod Hc occur in the hemolymph as aggregates of the basic 16S unit (24S, 37S, 48S, 53S and 62S). The 16S unit is a hexamer of 5S functional subunits. The specific aggregation forms, present in the hemolymph of the various animals, depend on the species (van Holde and van Bruggen, 1971;Markl, 1986;Ellerton et al., 1983). In the hemolymph of most crustacea, hexamers (16S) or dodecamers (24S) or both are found. However, the biological significance for the occurrence of such different aggregation forms is still controversial (Markl and Decker, 1992). Dissociation in functionally intact subunits can be accomplished by removing Ca 2ϩ and increasing the pH above 9.0 (Ellerton et al., 1983; van Holde and Miller, 1995). Various studies elucidate the subunit composition of crustacean Hc. In general, three subunits are found namely a, b and c subunits (Bak and Beintema, 1987;Jekel et al., 1988; Neuteboom et al., 1992;Markl, 1986). They are differently expressed in the various species (Mangum, 1993) and are necessary to guarantee the specific aggregation state (Markl and Decker, 1992). Hc bind oxygen as peroxide in a µϪη 2 :η 2 -coordination mode between the two Cu(II) ions ; while subunit...

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“…The (sub-)phylum Onychophora (velvet worms) includes the only extant representatives of the Lobopoda (13). The presence of respiratory proteins has been unknown among the Onychophora (14). Such proteins had been considered unnecessary because gas exchange of the Onychophora is mediated via tracheae (15).…”

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confidence: 99%

A hemocyanin from the Onychophora and the emergence of respiratory proteins

Kusche

Ruhberg

Burmester

2002

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

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The velvet worms (Onychophora) are considered living fossils and are closely related to the Euarthropoda. Onychophora possess a tracheal system for respiratory function, but oxygen-transport proteins have been considered unnecessary. Here, we show that the hemolymph of the Epiperipatus sp. (Onychophora: Peripatidae) contains an arthropod-type hemocyanin, demonstrating that such protein exists outside the Euarthropoda. Thus, the evolution of oxygen carriers preceded the divergence of the Onychophora and Euarthropoda and was most likely linked to the evolution of an efficient circulatory system in a low-oxygen environment. The cDNA of the Epiperipatus hemocyanin subunit comprises 2,287 bp and encodes for a protein of 641 aa (73.6 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.

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Hemocyanin—a current perspective

Cited by 168 publications

References 394 publications

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

Subunits composition and allosteric control in Carcinus aestuarii hemocyanin

A hemocyanin from the Onychophora and the emergence of respiratory proteins

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