title: Cloning and sequencing of Octopus dofleini hemocyanin cDNA: derived sequences of functional units Ode and Odf.
abstract: A number of additional cDNA clones coding for portions of the very large polypeptide chain of Octopus dofleini hemocyanin were isolated and sequenced. These data reveal two very similar coding sequences, which we have denoted "A-type" and "G-type." We have obtained complete A-type sequences coding for functional units Ode and Odf; consequently a total of three such unit sequences are now known from a single subunit of one molluscan hemocyanin. This presents the opportunity to make sequence comparisons within one hemocyanin subunit. Domains within one subunit show on the average 42% identity in amino acid residues; corresponding functional units from hemocyanins of different species show degrees of identity of 53-75%. Therefore, molluscan hemocyanins already existed before the individual molluscan classes diverged in the early Cambrian. Sequence comparisons of molluscan hemocyanins with arthropodan hemocyanins and tyrosinases allow us to identify the ligands of the "Copper B" site with high probability. Possible ligands for the "Copper A" site are proposed, based on sequence comparisons between molluscan hemocyanins and tyrosinases. Besides two histidine side chains, a methionine side chain might be involved in binding of Copper A, a result not in conflict with spectroscopic studies.
authors.affiliation: Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-6503.
authors.forename: W H
authors.initials: WH
authors.lastname: Lang
authors.forename: K E
authors.initials: KE
authors.lastname: van Holde
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D006433:Hemocyanins / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics; D014442:Monophenol Monooxygenase / Q000235:genetics; D049831:Octopodiformes / Q000235:genetics*; D015345:Oligonucleotide Probes; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
chemical_list: D015345:Oligonucleotide Probes; D004247:DNA; D006433:Hemocyanins; D014442:Monophenol Monooxygenase