title: Preparation and characterization of geodin. A betagamma-crystallin-type protein from a sponge.
abstract: Geodin is a protein encoded by a sponge gene homologous to genes from the betagamma-crystallins superfamily. The interest for this crystallin-type protein stems from the phylogenesis of porifera, commonly called sponges, the earliest divergence event in the history of metazoans. Here we report the preparation of geodin as a recombinant protein from Escherichia coli, its characterization through physico-chemical analyses, and a model of its 3D structure based on homology modelling. Geodin is a monomeric protein of about 18 kDa, with an all-beta structure, as all other crystallins in the superfamily, but more prone to unfold in the presence of chemical denaturants, when compared with other homologues from the superfamily. Its thermal unfolding, studied by far- and near-CD, and by calorimetry, is described by a two-state model. Geodin appears to be structurally similar in many respects to the bacterial protein S crystallin, with which it also shares a significant, albeit more modest stabilizing effect exerted by calcium ions. These results suggest that the crystallin-type structural scaffold, employed in the evolution of bacteria and moulds, was successfully recruited very early in the evolution of metazoa.
authors.affiliation: Department of Chemistry, University Federico II of Naples, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Giancola
authors.forename: Elio
authors.initials: E
authors.lastname: Pizzo
authors.forename: Antimo
authors.initials: A
authors.lastname: Di Maro
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Cubellis
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Alessio
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019791:Guanidine / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011161:Porifera / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013696:Temperature; D014508:Urea / Q000378:metabolism; D038204:beta-Crystallins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D038222:gamma-Crystallins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D038204:beta-Crystallins; D038222:gamma-Crystallins; C498129:geodin protein, E coli; D014508:Urea; D019791:Guanidine; D002118:Calcium