Haemocyanins in spiders, III. Chemical and physical properties of the proteins in Dugesiella and Cupiennius blood

HEMOLYMPH CHEMISTRY REFERENCE RANGES OF THE CHILEAN ROSE TARANTULA GRAMMOSTOLA ROSEA (WALKENAER, 1837) USING THE VETSCAN BIOCHEMISTRY ANALYZER BASED ON IFCC-CLSI C28-A3

The use of invertebrate hemolymph chemistry analysis has the potential to become a major diagnostic tool. The goal of this study was to generate statistically sound hemolymph reference ranges from healthy tarantulas. Hemolymph was drawn from wild caught, acclimatized, and apparently healthy female Chilean rose tarantulas Grammostola rosea (Walkenaer, 1837) ( n = 43) using a modified technique. Hemolymph samples were separately analyzed using the Avian-Reptilian Profile Plus reagent rotor for VetScan® for the following chemistries: aspartate aminotransferase, bile acids, creatine kinase, uric acid, glucose, total calcium, phosphorus, total protein, albumin, potassium, and sodium. With this method the authors were able to establish statistically sound reference ranges for aspartate aminotransferase, creatine kinase, glucose, phosphorus, and total protein. Further in situ studies will determine the practical usability of these values in the evaluation of tarantula health.

Vitellogenesis in spiders: first analysis of protein changes in different reproductive stages of Polybetes pythagoricus

Vitellogenesis represents one of the most vital processes of oviparous species during which various proteins, carbohydrates, and lipids are synthesized and stored inside the developing oocytes. Through analyzing protein changes in the midgut diverticula, hemolymph, and ovaries of females throughout the different vitellogenic stages of the spider Polybetes pythagoricus, we determined the origin of the different proteins involved in the formation of lipovitellins (LVs) along with the existence of a linkage between the hemocyanin and this vital process. An increase in the total protein content of the midgut diverticula, hemolymph, and ovary occurred throughout vitellogenesis followed by a decrease in those levels after laying. The presence of hemocyanin in egg and in LV2, as well as its accumulation in the ovary throughout the vitellogenesis process, was determined. Considering that all biologic processes depend on the correct structure and function of proteins, this study establishes, for the first time for the Order Araneae, the coexistence of three different origins of vitellogenesis-related proteins: one predominantly ovarian involving peptides of 120, 75, 46, and 30 kDa; another extraovarian one originated from the midgut diverticula and represented by a 170 kDa peptide, and a third hemolymphatic one, represented by the 67 kDa peptide.

Differences in Brachypelma albopilosa (Theraphosidae) hemolymph proteome between subadult and adult females

The changes in the hemolymph proteome of mygalomorph Brachypelma albopilosa females were examined for the first time in relation to their developmental stage (subadult and adult period). Seven distinct subunits of hemocyanin (a, b, c, d, e, f, and g chains), as well as actin were clearly identified and their sequence partly characterized using a combination of one- and two-dimensional gel electrophoresis and mass spectrometry. The different structures determined along with possible post-translational modifications may reflect a role of hemocyanin in molting, immunity, and reproduction. In addition, despite no precise identification, additional peptide sequences from eight protein bands (four bands >200 kDa and four bands in the 95-200 kDa mass range) were determined. As reported in other spider species, the putative corresponding structures are the coagulogen protein and/or lipoproteins (HDL-1, HDL-2, VHDL) for which quantitative differences between adult and subadult individuals could be related to the molting process and/or cuticle lipid and protein composition according to the developmental stage.

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

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 4x6-meric hemocyanins. The thalassinidean hemocyanin appears similar in size but different in structural organization compared to the chelicerate 4x6-mer. Ultracentrifuge analyses on the purified protein revealed a sedimentation coefficient of 39S, typical of 4x6 hemocyanins. Electron micrographs are in agreement with a model in which four 2x6-meric building blocks are arranged in a tetrahedron-like quaternary structure and not in the quasi-square-planar orientation characteristic of the chelicerate protein. Size-exclusion chromatography-fast protein chromatography analysis showed elevated instability of the protein in absence of divalent ions or at pH values higher than 8.0. This analysis also shows that the dissociation of the U. pusilla 4x6-meric hemocyanin into hexamers occurs without any intermediate 2x6-meric state, in contrast with the dissociation profile of the chelicerate protein exhibiting several dissociation intermediates. The oxygen-binding properties of U. pusilla hemocyanin were studied to disclose possible effects by the typical allosteric effectors that modulate the functional properties of crustacean hemocyanin. A marked Bohr and lactate effect, but no significant influence of urate, on the oxygen affinity of U. pusilla hemocyanin were found.

Arachnid lipoproteins: comparative aspects

Findings on hemolymph lipoproteins in the class Arachnida are reviewed in relation to their lipid and protein compositions, hydrated densities, the capacity of apoproteins to bind lipids, and the influence of xenobiotics on their structures and functionality. The occurrence of hemolymphatic lipoproteins in arachnids has been reported in species belonging to the orders Araneida, Scorpionida, Solpugida and Acarina. However, lipoproteins were properly characterized in only three species, Eurypelma californicum, Polybetes pythagoricus and Latrodectus mirabilis. Like insect and crustaceans the arachnids examined contain high density lipoproteins (HDLs) as predominant circulating lipoproteins. Although in most arachnids these particles resemble those of insect HDLs called "lipophorins", in two arachnid species they differ from lipophorins in their apoproteins, total mass and lipid composition. The hemolymph of P. pythagoricus and L. mirabilis contains another HDL of higher density, while P. pythagoricus and E. californicum hemolymph contain a third lipoprotein of very high density (VHDL). Composition of arachnid lipoproteins regarding apoprotein classes as well as lipid classes differ among species. Hemocyanin, in addition to the classical role of this protein as respiratory pigment, is presented here performing the function of apolipoprotein in some arachnid species. Reports on experiments demonstrating the capacity of hemocyanin to bind neutral and polar lipid classes, including ecdysteroids, are commented. Recent works about the changes evoked by a phosphorous pesticide on the structures and functionality of spider lipoproteins are also reviewed.

Characterization of the carbohydrate moieties of the functional unit RvH1-a of Rapana venosa haemocyanin using HPLC/electrospray ionization MS and glycosidase digestion

The primary structures of two biantennary N -glycans of the glycoprotein Rapana venosa (marine snail) haemocyanin were determined. Two different structural subunits have been found in R. venosa haemocyanin: RvH1 and RvH2. The carbohydrate content of the N-terminal functional unit RvH1-a of RvH1 was studied and compared with the N-terminal functional unit RvH2-a of RvH2. Oligosaccharide fragments were released from the glycoprotein by Smith degradation of a haemocyanin pronase digest and separated on a Superdex 300 column. The glycopeptide fragments, giving a positive reaction for the orcinol/H2SO4 method, were separated by HPLC. In order to determine the linked sugar chains to the hinge glycopeptides isolated from the functional unit RvH1-a, several techniques were applied, including capillary electrophoresis, matrix-assisted laser desorption ionization-MS and electrospray ionization-MS in combination with glycosidase digestion. On the basis of these results and amino acid sequence analysis, we concluded that the functional unit RvH1-a contains 7% oligosaccharides N-glycosidically attached to Asn262 and Asn401, and the following structures were suggested:[structure: see text]

Complete hemocyanin subunit sequences of the hunting spider Cupiennius salei: recent hemocyanin remodeling in entelegyne spiders

Hemocyanins are large copper-containing respiratory proteins found in many arthropod species. Scorpions and orthognath spiders possess a highly conserved 4 x 6-mer hemocyanin that consists of at least seven distinct subunit types (termed a to g). However, many "modern" entelegyne spiders such as Cupiennius salei differ from the standard arachnid scheme and have 2 x 6-mer hemocyanins. Here we report the complete primary structure of the 2 x 6-mer hemocyanin of C. salei as deduced from cDNA sequencing, gel electrophoresis, and matrix-assisted laser desorption spectroscopy. Six distinct subunit types (1 through 6) and three additional allelic sequences were identified. Each 1 x 6-mer half-molecule most likely is composed of subunits 1-6, with subunit 1 linking the two hexamers via a disulfide bridge located in a C-terminal extension. The C. salei hemocyanin subunits all belong to the arachnid g-type, whereas the other six types (a-f) have been lost in evolution. The reconstruction of a complex hemocyanin from a single g-type subunit, which commenced about 190 million years ago and was completed about 90 million years ago, might be explained by physiological and behavioral changes that occurred during the evolution of the entelegyne spiders.

Carbohydrate composition of Carcinus aestuarii hemocyanin

The hemocyanin of the crab Carcinus aestuarii contains a carbohydrate moiety that represents 1.6% of protein mass. This carbohydrate content is higher than that exhibited by other arthropod hemocyanins so far investigated. By combination of FPLC ion exchange chromatography and reverse-phase HPLC, the native oligomeric protein can be resolved into three major and one minor electrophoretically pure fractions that are found to be homogeneous by N-terminal sequencing and correspond to the subunit polypeptide chains. Sugar analysis on the different subunits reveals that the subunit referred to as Ca2 is glycosylated, with a carbohydrate content of 6.3%. By Ca2 trypsin digestion, separation of glycopeptides, and amino acid sequencing, three consensus sequences for O-glycosylation and one for N-glycosylation were found. MALDI-MS was applied for the determination of the molecular masses of the various glycopeptides and peptides after removal of carbohydrates by neuraminidase and alpha-N-acetylgalactosaminidase.

Oxygen transport proteins: I. Structure and organization of hemocyanin from scorpion (Buthus sindicus)

Scorpions are regarded as the oldest terrestrial arthropods. Scorpion Buthus sindicus (Buthidae) is commonly found in Pakistan and the Mediterranean region. The hemolymph of most arthropods contains large multisubunit, extracellular metalloprotein commonly known as hemocyanin which performs the important function of oxygen transport. The literature available to date shows that no attempt has been made to study hemocyanins or hemolymph proteins from this species. This communication presents the isolation, characterization and partial structural studies on hemocyanin from scorpion Buthus sindicus. (1) The hemolymph was collected by cardiac puncture, centrifuged and subjected to polyacrylamide gel electrophoresis and isoelectric focussing. (2) Crude hemolymph was subjected to gel filtration and high performance ion-exchange chromatography. (3) Purified hemocyanin subunits Bsin 1, 2 and 3 have been analysed for their amino acid composition and N-terminal sequence. The sequence homology was determined by comparison with other arthropod hemocyanin. The results are discussed.

Tarantula (Eurypelma californicum) venom, a multicomponent system

The venom of the tarantula Eurypelma californicum was analysed biochemically, the components were isolated and characterized. The pH value of the crude venom is 5.3 +/- 0.3. After dilution with distilled water, UV-absorption spectra showed a single maximum at 258 nm (pH ca. 7.0). A second maximum at 328 nm emerged above pH 8.0. Protein concentration of the venom is ca. 65 mg/ml. After Coomassie staining SDS-PAGE patterns show three major bands with apparent molecular masses around 40 kDa, 4.3 kDa and 1.3 kDa besides some weak high molecular protein bands. The following low-molecular mass constituents were determined in the crude venom: ATP, ADP, AMP, glutamic acid, aspartic acid, gamma-aminobutyric acid, glucose and the ions potassium, sodium, calcium, magnesium and chloride; the osmolality was 361 micro0smol/ml. The LD50 value for female cockroaches was 0.15 microliters venom per g body weight and for male cockroaches 0.4 microliters venom per g body weight. Separation of the crude venom by gel chromatography yielded four elution peaks. Peak I contains the enzyme hyaluronidase. The activity is 200-900 U/microliters. Peak II contains a mixture of toxic peptides. Peak III contains the 1.3-kDa components of SDS-PAGE and peak IV mainly contains ATP. Venom proteins including the enzyme hyaluronidase were precipitated by 5% trichloroacetic acid. The supernatant was separated by HPLC into 13 fractions. Fraction 1 contains glutamic acid, aspartic acid, gamma-aminobutyric acid and ATP; fraction 2 contains ATP, ADP and AMP as well as a component 2' visible in SDS-PAGE as 1.3-kDa band and consisting of spermine and tryptophan; fraction 3 contains ATP and an unknown component 3'; fractions 4-6 also show a 1.3-kDa band in SDS-PAGE, fraction 4 being tyrosylspermine and fractions 5 and 6 containing compounds of spermine and aromatic molecules; fraction 7 contains a peptide which lacks aromatic amino acids, it was sequenced from the N-terminus; fractions 8-13 contain very similar toxic peptides. The peptides in fractions 11 and 12, labeled ESTX for Eurypelma spider toxin, were cleaved with different enzymes and sequenced. They differ in one amino acid in position 26. Homologies with scorpion toxins and with a toxin of the spider Segestria florentina were found.

Hemocyanins in spiders. XXII. Range of allosteric interaction in a four-hexamer hemocyanin. Co-operativity and Bohr effect in dissociation intermediates

The range of allosteric interaction in the 24-meric hemocyanin from the tarantula Eurypelma californicum was studied by measuring the oxygen-binding properties of defined oligomeric fragments. Dissociation intermediates comprising 19, 12, 7 or 6 subunits were obtained by incubation of native hemocyanin with 10 mM-cysteine at pH 4.4, with 40 mM-dithiothreitol at pH 7 or 8, by short-term alkaline (pH 9.6) treatment or by treatment with 4 M-urea. These could be stabilized by returning to neutral buffer conditions and, in the case of the dodecamer, by carboxymethylation. Conditions were chosen so that part of the starting material remained intact to serve as control in the oxygen-binding measurements. Oxygen equilibrium curves were obtained by a very sensitive fluorimetric/polarographic method. Oxygen affinity and the magnitude of the Bohr effect remain constant from the hexamer up to the control four-hexamer. Co-operativity, in contrast, increases with aggregate size in two steps: n (hexamer) = n (heptamer) less than n (dodecamer) = n (19-mer) less than n (4-hexamer). The characteristic pH-dependence of nH is absent in the hexa- and heptamer but is weakly indicated in the dodecamer, and fully established in the four-hexamer. Results from different preparations are highly consistent, if nH is expressed as a percentage of the control values. Full co-operativity is reached only in the four-hexamer, disproving the dodecameric half-molecule (the smallest repeating unit) as the allosteric unit. The stepwise increase in co-operativity appears to be correlated with higher levels of symmetry in the hierarchy of quaternary structure.

Immunological correspondence between arthropod hemocyanin subunits. II. Xiphosuran (Limulus) and spider (Eurypelma, Cupiennius) hemocyanin

The hemocyanins of the horseshoe crab Limulus polyphemus (48-mer), the tarantula Eurypelma californicum (24-mer), and the lycosid spider Cupiennius salei (dodecamer, hexamer) were dissociated into subunits, the subunits isolated and studied by two-dimensional immunoelectrophoresis for interspecific cross-reactivities. Among the subunits a to g of Eurypelma on the one side, and I to VI of Limulus on the other, a number of cross-reactions were obtained which agree with the topologic subunit positions in the published models of quaternary structure: a = II, b-c = V-VI, d = IV, e = I, f = IIIb, g = IIIa (IIa). However, cross-reactivity was only strong in the following combinations: a/II, d/IV, b-c/V-VI (the monomers of the two heterodimers could not be correlated individually). A rather weak cross-reaction was obtained in the case of e/I and g/IIIa (IIa); a cross-reaction between f and IIIb was almost undetectable. On the other hand, f/IV clearly cross-reacted, and so did e/IIIa (IIa), which apparently is not in agreement with the two models of quaternary structure. These unexpected relationships, however, indicate the possible phylogeny of the subunits. Antiserum against Cupiennius hemocyanin precipitated subunit f of Eurypelma and subunit IV of Limulus and, moreover, revealed common antigen determinants present on these subunits. Denaturation of hemocyanin subunits of the three species with 8M urea yielded a completely different immunological behavior in that in all intra- and interspecific combinations the reaction of immunological identity was obtained. The published models of quaternary structure and a possible subunit phylogeny of cheliceratan hemocyanins is discussed in view of the present results and the results of the preceding paper. [Markl, J. et al. (1984) Hoppe-Seyler's Z. Physiol. Chem. 365, 619-631.]

Immunological correspondence between arthropod hemocyanin subunits. I. Scorpion (Leiurus, Androctonus) and spider (Eurypelma, Cupiennius) hemocyanin

The hemocyanins of the scorpions Leiurus quinquestriatus and Androctonus australis, the tarantula Eurypelma californicum (all 24-mers), and the lycosid spider Cupiennius salei (dodecamer) were dissociated into subunits, the subunits isolated and studied by two-dimensional immunoelectrophoresis for interspecific cross-reactivities. Androctonus hemocyanin yielded a pattern of 8 subunit types in agreement with data from Lamy et al. (1979, Arch. Biochem. Biophys. 193, 140-149). Leiurus hemocyanin is also composed of 8 immunologically distinct subunits which could be assigned to the pattern of Androctonus in a subunit-to-subunit correlation. The subunit designations 1 to 6 of Lamy et al. could be adopted for both scorpion hemocyanins; however, in the present communication, Lamy's subunits 3A/3B are designated as 3'/3", because we could not unequivocally decide if 3' = 3A and 3" = 3B or vice versa. The 7 subunit types a to g of Eurypelma hemocyanin could be correlated with the scorpion hemocyanin subunits as follows: a = 3', b = 5B, c = 3C, d = 5A, e = 6, f = 2, g = 4. Additional cross-reactivities were detected between e/4, and f/5A, respectively. No subunit of Eurypelma hemocyanin is homologous to scorpion 3", which could not be precipitated by anti-Eurypelma antiserum. Antiserum against Cupiennius hemocyanin precipitated subunit f of Eurypelma and subunits 2 and 5A of scorpion hemocyanin. The published models of quaternary structure and a possible subunit phylogeny of arachnidan hemocyanins are discussed in view of the present results.

Hemocyanins in spiders, XIX. Complete amino-acid sequence of subunit d from Eurypelma californicum hemocyanin, and comparison to chain e

The complete primary structure of subunit d of the hemocyanin from the tarantula Eurypelma californicum was determined by manual micro sequencing. Subunit d of Mr = 73000 is split about in the middle of the chain during limited trypsinolysis, only one single bond being attacked. The whole chain contains 14 methionine residues and after cyanogen bromide cleavage 15 peptides could be isolated by gel and ion exchange chromatography and high pressure liquid chromatography. The cyanogen bromide peptides and the large (Mr = 34000 and 37000, respectively) fragments resulting from limited trypsinolysis, were further cleaved with trypsin, chymotrypsin, Staphylococcus aureus proteinase, formic acid, and Astacus fluviatilis proteinase, the latter being very useful in obtaining certain overlapping peptides. The total chain length is 627 residues. Carbohydrate side chains were not found. The sequence is discussed with respect to the gross physical properties of the subunit, to homologies with subunit e and the cleavage specifities of the enzymes employed.

Hemocyanins in Spiders, XVIII. Complete amino-acid sequence of subunit e from Eurypelma californicum hemocyanin

The complete amino-acid sequence of subunit e of the hemocyanin from the tarantula, Eurypelma californicum, was determined by a combination of manual and automated methods. By limited proteolysis with chymotrypsin, two large fragments (e-CHn 29 and e-CHn 42) were obtained. The large peptides were further cleaved with cyanogen bromide, trypsin (with and without prior blocking of lysine residues), chymotrypsin, Staphylococcus aureus proteinase, Astacus fluviatilis proteinase, or 25% formic acid. The complete chain comprises 621 residues. A remarkable feature of the sequence is a hexapeptide -His-His-Trp-His-Trp-His- which is believed to take part in the binding of copper.

Hemocyanins in spiders, XIV. Subunit composition of dissociation intermediates and its bearing on quaternary structure of Eurypelma hemocyanin

The 37 S hemocyanin (24 subunits of 7 types) isolated from the tarantula, Eurypelma californicum, was dissociated partially by various agents and the dissociation intermediates analyzed for their subunit composition by crossed immunoelectrophoresis. The subunit composition of the native hemocyanin was reexamined and the pending problem of the ratio between subunits a and g (= c2) clarified. The subunits are present in the ratio of a:b:c:d:e:f:g = 4:2:2:4:4:4:4. Breakdown products were shown to contain 19 (20?), 16, 12, 8, 7 and 6 polypeptide chains (possibly, there is also a 15-mer). The 19-mer is formed by removal of 5 monomeric subunits from one of the constituent hexamers of the native (4 x 6) hemocyanin, the 16-mer by losing one further copy each of e, f and g. The dodecamer is formed by cleavage with 2-mercaptoethanol and represents a half-molecule. The octamer could not be clearly analyzed but probably contains one copy of chain d more compared to the heptamer. The heptamer represents a one-quarter hemocyanin with one additional polypeptide chain sticking out of the hexameric structure. This can be either subunit b or c of the heterodimer bc. Only one type of hexamer was obtained after cleavage of the 37 S hemocyanin with 4M urea, containing one copy each of chains a, b, d, e, f and g. It is concluded that the 37 S hemocyanin is composed of two identical dodecameric halves linked by dimerization of subunit f, and that each half-molecule is constituted by two non-identical though similar hexamers, both encompassing a complete set of subunits a, d, e, f and g, but differing in their share of the rather stable, the 'c'-hexamer unstable. The relative positions of some of the subunits within the native oligomer are discussed.

Hemocyanins in spiders, IX. Homogeneity, subunit composition and the basic oligomeric structure of Eurypelma californicum hemocyanin

37S hemocyanin isolated from the tarantula Eurypelma californicum was subjected to a variety of fractionation procedures: Electrophoresis in polyacrylamide gels, isoelectrofocusing, and ion exchange chromatography. Single fractions were dissociated at alkaline pH and/or by sodium dodecyl sulfate and the resulting subunits separated by polyacrylamide gel electrophoresis in gradient slab gels followed, in many cases, by quantitative estimation of the subunit bands. In addition, crossed immunoelectrophoresis was employed to analyze the subunit composition. Separation of the native hemocyanin into fractions with different subunit composition was not observed. Also, hemocyanin samples taken from individual spiders showed a strikingly uniform composition. It is concluded that Eurypelma hemocyanin is homogeneous for all practical means. This implies that the seven different polypeptide chains described previously for Eurypelma hemocyanin all take part in the formation of the 24 subunits, 37S oligomeric molecule. By monitoring chromatographic effluents at 280 nm, scanning stained electrophoresis gels and determining peak areas in these experiments and in crossed immunoelectrophoresis, the relative quantities of the seven different polypeptide chains in the whole molecule were determined as follows (number per 37S molecule): 6a, 2b, 2c2, 2c4, 4d, 4e, 4f. The ratio between a and c2 (6:2) is the least well established. Since 7 different polypeptide chains are incorporated, the hexameric molecule cannot represent the basic oligomeric structure in tarantula hemocyanin, but probably the dodekamer. If Eurypelma hemocyanin is incubated with sucrose, partial dissociation occurs, yielding a fragment sedimenting with ca. 28S. This process is reversible. The 28S fragment still contains all subunit species; it is thought to represent a (3 x 6) or closely related structure. The implications of this finding with respect to the symmetry of the native hemocyanin molecule are discussed.

Application of calculated sedimentation ratios in the specification of models for protein dimers, trimers, tetramers and pentamers

In the preceding paper a systematic method for delineating quaternary structures compatible with the sedimentation behaviour of oligomeric assemblies was developed. In this companion paper the approach is illustrated by its application to a number of oligomeric proteins, namely beta-lactoglobulin, aminoacyl transferase, succinic semialdehyde dehydrogenase, arginine decarboxylase, and the arthropod hemocyanins. Structures of these proteins based on comparisons of calculated and experimental sedimentation coefficients are presented and, wherever possible, compared with those obtained by other techniques. The usefulness and limitations of the method are assessed. It is concluded that the sedimentation analysis will usually yield a reasonably good representation of the mode of assembly of protein molecules in oligomeric structures if accurate experimental data are available. A high degree of resolution of structural detail is not expected and since, in addition, the sedimentation ratio method is seldom definitive to one structure, it is most valuable when used in a conformatory or eliminative way with results from techniques more specifically designed for structure determination.

Hemocyanins in spiders, VII. Immunological comparison of the subunits of Eurypelma californicum hemocyanin

The isolated subunites of Eurypelma californicum hemocyanin were studied by aid of antibodies raised against whole, dissociated hemocyanin. The proportion of impurities was found to be low in almost all subunits. There was no cross reaction between the individual chains, and the total number of antigenically different subunits was found to be seven, confirming results obtained by different methods. If an artificial mixture prepared from purified subunits is compared to whole, dissociated hemocyanin, an overall very similar pattern is obtained but differences appear which are due to specific interaction.--The dimeric subunit 4D was shown to be a heterodimer (asymmetric dimer) composed of chains b and c4.

Hemocyanins in spiders, VI[1]. Comparison of the polypeptide chains of Eurypelma californicum hemocyanin

The subunits of the hemocyanin from the tarantula, Eurypelma californicum, were isolated, following dissociation at pH 9.6, by a sequence of chromatographic and electrophoretic steps. Fraction 2 (containing two chains, a and c2) and the constituent polypeptide chains of the dimeric subunit 4D (b and c4) were resolved by anion exchange chromatography at pH 8.9 and 6.5, respectively. Since c2 and c4 have different electrophoretic mobilities in polyacrylamide gradient gels, the total number of different polypeptide chains is seven. The amino acid compositions of the seven chains are reported. There are major differences for at least half of the amino acids, while more consistent proportions become evident, if the amino acids are grouped by types of side chains. The N-terminal amino acid is proline in the case of chains b and e,, while no end group called be detected in any of the other chains by different methods. The C-terminal end group was found to be valine in both chains d and e. Cleavage by 70% formic acid, and by cyanogen bromide in formic acid results in fragmentation patterns distinct for each chain. After cyanogen bromide cleavage, the two largest peptides of each chain are of molecular weight near 2400. Tryptic fingerprints also reveal significant differences between all chains. Subunit heterogeneity of Eurypelma hemocyanin is clearly not the consequence of secondary modifications, but resides in major differences of the amino acid sequences.