title: Subunit sequences of the 4 x 6-mer hemocyanin from the golden orb-web spider, Nephila inaurata.
abstract: The transport of oxygen in the hemolymph of many arthropod and mollusc species is mediated by large copper-proteins that are referred to as hemocyanins. Arthropod hemocyanins are composed of hexamers and oligomers of hexamers. Arachnid hemocyanins usually form 4 x 6-mers consisting of seven distinct subunit types (termed a-g), although in some spider taxa deviations from this standard scheme have been observed. Applying immunological and electrophoretic methods, six distinct hemocyanin subunits were identified in the red-legged golden orb-web spider Nephila inaurata madagascariensis (Araneae: Tetragnathidae). The complete cDNA sequences of six subunits were obtained that corresponded to a-, b-, d-, e-, f- and g-type subunits. No evidence for a c-type subunit was found in this species. The inclusion of the N. inaurata hemocyanins in a multiple alignment of the arthropod hemocyanins and the application of the Bayesian method of phylogenetic inference allow, for the first time, a solid reconstruction of the intramolecular evolution of the chelicerate hemocyanin subunits. The branch leading to subunit a diverged first, followed by the common branch of the dimer-forming b and c subunits, while subunits d and f, as well as subunits e and g form common branches. Assuming a clock-like evolution of the chelicerate hemocyanins, a timescale for the evolution of the Chelicerata was obtained that agrees with the fossil record.
authors.affiliation: Institute of Zoology, Johannes Gutenberg University, Mainz, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Averdam
authors.forename: Jürgen
authors.initials: J
authors.lastname: Markl
authors.forename: Thorsten
authors.initials: T
authors.lastname: Burmester
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D019143:Evolution, Molecular; D006433:Hemocyanins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007122:Immunoelectrophoresis; D008969:Molecular Sequence Data; D010802:Phylogeny; D013112:Spiders / Q000737:chemistry / Q000235:genetics*
chemical_list: D006433:Hemocyanins