The amino acid sequence of the hemocyanin subunit c from the spiny lobster, Panulirus interruptus, has been determined. The elucidation was mainly based on three digests, with CNBr, trypsin and endoproteinase Glu-C, respectively. Additional evidence was obtained by sequencing of peptides from an endoproteinase Lys-C digest. Subunit c is a polypeptide with 661 amino acid residues and with a carbohydrate group attached to residue 476 in the third domain. No heterogeneity was observed. The degree of identity with subunit a is 59%. Some differences with subunit a are an Nterminal extension of six residues, a one-residue C-terminal extension, and a three-residue deletion. Furthermore, carbohydrate attachment is in a different position, as are most half-cystine residues. Limited trypsinolysis resulted in cleavage at the same site as in subunits a and b.Hemocyanins are copper-containing oxygen carriers occurring freely dissolved in the hemolymph of many molluscs and arthropods. Arthropod hemocyanins consist of hexamers or multihexamers with subunits of about 75 kDa, each of which contains one binuclear copper site The three-dimensional structure of P. interruptus hemocyanin has been determined by X-ray diffraction at a resolution of 0.32 nm, with crystals consisting of a mixture of a and b in roughly equal amounts [6, 71. Each subunit is folded into three domains. The first and the second domain are mainly globular, the third domain contains a sevenstranded P-barrel. The second domain contains the binuclear oxygen-binding site.

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Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and mollusts. The amino acid sequence of subunit a of Panulirus interruptus hemocyanin (657 residues) has been completed and fitted to the electron-density map (3.2 A resolution). Comparison of amino acid sequence data for several different hemocyanin subunits of arthropod species indicated that the general features of the polypeptide architecture as found in spiny lobster hemocyanin occur in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, 540-600 million years ago. (Panulirus interruptus)Hemocyanin Amino acid sequence Molecular evolution

Human alpha-lactalbumin has not been described as a glycoprotein, despite the fact that several alpha-lactalbumins of both ruminant and nonruminant species are known to be glycosylated. In all these species the glycosylation site is the 45Asn in the usual triplet 45Asn-Gly/Gln-47Ser. We have found that human alpha-lactalbumin is glycosylated and the glycosylation site has been determined by protein sequencing and mass spectrometry. We report an unusual glycosylation site at 71Asn in the triplet 71Asn-Ile-73Cys, which is conserved in all known alpha-lactalbumins except red-necked wallaby. That a relatively small proportion of the protein is glycosylated (about 1%) may reflect the importance of this region of the protein sequence to the molten globule state of alpha-lactalbumin.