Search results for "hemocyanin"

Primary structure and unusual carbohydrate moiety of functional unit 2-c of keyhole limpet hemocyanin (KLH)

1999

Abstract The complete amino acid sequence of the Megathura crenulata hemocyanin functional unit KLH2-c was determined by direct sequencing and matrix-assisted laser desorption ionization mass spectrometry of the protein, and of peptides obtained by cleavage with EndoLysC proteinase, chymotrypsin and cyanogen bromide. This is the first complete primary structure of a functional unit c from a gastropod hemocyanin. KLH2-c consists of 420 amino acid residues. Circular dichroism spectra indicated approx. 31% β-sheet and 29% α-helix contents. A multiple sequence alignment with other molluscan hemocyanin functional units revealed average identities between 41 and 49%, but 55% in case of Octopus he…

Assessing divergence time of Spirulida and Sepiida (Cephalopoda) based on hemocyanin sequences

2011

Abstract The phylogenetic position of the mesopelagic decabrachian cephalopod Spirula is still a matter of debate. Since hemocyanin has successfully been used to calibrate a molecular clock for many molluscan species, a molecular clock was calculated based on this gene with special attention to the cephalopod genera Spirula and Sepia. The obtained partial sequence comprising ca., one third (3567 bp) of the complete gene is similar to that of Sepia officinalis. The molecular clock was calibrated using the splits of Gastropoda–Cephalopoda (ca. 550 ± 50 mya) and Heterobranchia–Vetigastropoda (ca. 380 ± 10 mya). The resulting hemocyanin-based molecular clock is stable, and the estimated diverge…

Modeling techniques for analysing conformational transitions in hemocyanins by small-angle scattering of X-rays and neutrons.

2004

Cops and robbers: putative evolution of copper oxygen-binding proteins.

2000

Two closely related copper proteins, phenoloxidase and haemocyanin, are known to be involved in different physiological functions such as the primary immune response and oxygen transport. Although the proteins differ structurally, they have the same active site by which dioxygen is bound. Recent results reveal that haemocyanin also exhibits phenoloxidase activity. A scenario is proposed for the evolutionary relationships among copper oxygen-binding proteins (COPs).

Temperature adaptation influences the aggregation state of hemocyanin from Astacus leptodactylus.

2000

When Astacus leptodactylus were kept at various temperatures for several weeks, different ratios between di-hexameric and hexameric hemocyanins were observed in their hemolymph. The higher the temperature the more hexamers were present. This long-term adaptation to different temperatures or/and to temperature-induced pH-shifts as observed in the hemolymph has different effects on the expression of subunit types building up hexamers and those which covalently link two hexamers within the di-hexamers. The oxygen binding behaviour of di-hexameric hemocyanins from cold and warm adapted animals do not show differences with respect to affinity, Bohr effect and cooperativity.

Origin and evolution of arthropod hemocyanins and related proteins.

2002

Arthropod hemocyanins are large, multimeric, (n x 6) copper-containing proteins that deliver oxygen in the haemolymph of many chelicerate, crustacean, myriapod, and also possibly some insect species. The arthropod hemocyanins belong to a large protein superfamily that also includes the arthropod phenoloxidases, certain crustacean and insect storage proteins (pseudo-hemocyanins and hexamerins), and the insect hexamerin receptors. Here I summarise the present knowledge of the origin, functional adaptations, and evolution of these proteins. Arthropod and mollusc hemocyanins are, if at all, only distantly related. As early as in the arthropod stem line, the hemocyanins emerged from a phenoloxid…

Cryo-negative staining

1998

Abstract A procedure is presented for the preparation of thin layers of vitrified biological suspensions in the presence of ammonium molybdate, which we termcryo-negative staining. The direct blotting of sample plus stain solution on holey carbon supports produces thin aqueous films across the holes, which are routinely thiner than the aqueous film produced by conventional negative staining on a continuous carbon layer. Because of this, a higher than usual concentration of negative stain (ca. 16% rather than 2%) is required for cryo-negative staining in order to produce an optimal image contrast. The maintenance of the hydrated state, the absence of adsorption to a carbon film and associate…

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

2006

The structural properties of the hemocyanin isolated from the Mediterranean mud shrimp, Upogebia pusilla (Decapoda: Thalassinidea), were investigated. Our intent was to make use of the U. pusilla case to perform a structural comparison between crustacean and chelicerate 4×6-meric hemocyanins. The thalassinidean hemocyanin appears similar in size but different in structural organization compared to the chelicerate 4×6-mer. Ultracentrifuge analyses on the purified protein revealed a sedimentation coefficient of 39S, typical of 4×6 hemocyanins. Electron micrographs are in agreement with a model in which four 2×6-meric building blocks are arranged in a tetrahedron-like quaternary structure and …

Influence of antibody binding on oxygen binding behavior of Panulirus interruptus hemocyanin

1997

Oxygen binding behavior of monomeric subunit a and the hexameric form of this subunit of hemocyanin of Panulirus interruptus is influenced by the binding of various monoclonal antibodies. These antibodies react with other surface parts of the subunit than its second domain in which the oxygen binding site is located. The influence of three monoclonal antibodies and their antigen binding fragments (F-ab) has been investigated. Two antibodies increase the oxygen affinity of monomeric hemocyanin from that observed in its low affinity T-state, while the third has little influence on this property. F-ab fragments abolish almost completely the cooperativity of oxygen binding by the hexameric hemo…

Subunits composition and allosteric control in Carcinus aestuarii hemocyanin

1998

Carcinus aestuarii hemocyanin (Hc) exists in two aggregation forms at pH 7.5 and 20 mM Ca2+: 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 …