title: A novel interdomain interface in crystallins: structural characterization of the βγ-crystallin from Geodia cydonium at 0.99 Å resolution.
abstract: The βγ-crystallin superfamily includes highly diverse proteins belonging to all of the kingdoms of life. Based on structural topology, these proteins are considered to be evolutionarily related to the long-lived βγ-crystallins that constitute the vertebrate eye lens. This study reports the crystallographic structure at 0.99 Å resolution of the two-domain βγ-crystallin (geodin) from the sponge Geodia cydonium. This is the most ancient member of the βγ-crystallin superfamily in metazoans. The X-ray structure shows that the geodin domains adopt the typical βγ-crystallin fold with a paired Greek-key motif, thus confirming the hypothesis that the crystallin-type scaffold used in the evolution of bacteria and moulds was recruited very early in metazoans. As a significant new structural feature, the sponge protein possesses a unique interdomain interface made up by pairing between the second motif of the first domain and the first motif of the second domain. The atomic resolution also allowed a detailed analysis of the calcium-binding site of the protein.
authors.affiliation: Department of Chemical Sciences, University of Naples 'Federico II', Via Cintia, I-80126 Napoli, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vergara
authors.forename: Marco
authors.initials: M
authors.lastname: Grassi
authors.forename: Filomena
authors.initials: F
authors.lastname: Sica
authors.forename: Elio
authors.initials: E
authors.lastname: Pizzo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Alessio
authors.forename: Lelio
authors.initials: L
authors.lastname: Mazzarella
authors.forename: Antonello
authors.initials: A
authors.lastname: Merlino
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D047231:Geodia / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D017510:Protein Folding
chemical_list: D003459:Crystallins
keywords: Greek-key motif; Trp corner; Tyr corner; atomic resolution; calcium binding; crystallins; domain interactions; folding