title: Cupredoxin-like domains in haemocyanins.
abstract: Haemocyanins are multimeric oxygen transport proteins, which bind oxygen to type 3 copper sites. Arthropod haemocyanins contain 75-kDa subunits, whereas molluscan haemocyanins contain 350-400-kDa subunits comprising seven or eight different 50 kDa FUs (functional units) designated FU-a to FU-h, each with an active site. FU-h possesses a tail of 100 amino acids not present in the other FUs. In the present study we show by X-ray crystallography that in FU-h of KLH1 (keyhole-limpet-haemocyanin isoform 1) the structure of the tail domain is cupredoxin-like but contains no copper. The copper-free domain 3 in arthropod haemocyanin subunits has also recently been reinterpreted as being cupredoxin-like. We propose that the cupredoxin-like domain in both haemocyanin types once served to upload copper to the active site of the oxygen-binding domain.
authors.affiliation: Institut für Molekulare Biophysik, Johannes Gutenberg-Universität, Jakob Welder Weg 26, 55128 Mainz, Germany. elmar.jaenicke@uni-mainz.de
authors.forename: Elmar
authors.initials: E
authors.lastname: Jaenicke
authors.forename: Kay
authors.initials: K
authors.lastname: Büchler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Markl
authors.forename: Heinz
authors.initials: H
authors.lastname: Decker
authors.forename: Thomas R M
authors.initials: TR
authors.lastname: Barends
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001400:Azurin / Q000737:chemistry; D001665:Binding Sites / Q000235:genetics; D003300:Copper / Q000737:chemistry; D018360:Crystallography, X-Ray; D049851:Gastropoda / Q000737:chemistry* / Q000235:genetics; D006433:Hemocyanins / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: C050107:cupredoxin; D001400:Azurin; D003300:Copper; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin