title: The structure of avian eye lens delta-crystallin reveals a new fold for a superfamily of oligomeric enzymes.
abstract: The crystal structure of turkey delta-crystallin, a principal soluble components of the avian lens, has been determined to a resolution of 2.5 A. It is a tetramer, of 200,000 M(r), with 222 symmetry. The subunit has a new fold composed of three mainly alpha-helical domains. One domain is a bundle of five long helices which forms a 20-helix bundle at the core of the tetramer. delta-crystallin shares approximately 90% sequence identity with the enzyme argininosuccinate lyase (EC 4.3.2.1), indicating that it is an example of a 'hijacked' enzyme. It is also distantly related to the class II fumarases, aspartases, adenylosuccinases and 3-carboxy-cis,cis-muconate lactonising enzyme. The structure reveals a putative active-site cleft which is located on the boundary between three subunits of the tetramer. This is the first three-dimensional structure of a representative of this superfamily of enzymes.
authors.affiliation: Laboratory of Molecular Biology, Birkbeck College, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Simpson
authors.forename: O
authors.initials: O
authors.lastname: Bateman
authors.forename: H
authors.initials: H
authors.lastname: Driessen
authors.forename: P
authors.initials: P
authors.lastname: Lindley
authors.forename: D
authors.initials: D
authors.lastname: Moss
authors.forename: S
authors.initials: S
authors.lastname: Mylvaganam
authors.forename: E
authors.initials: E
authors.lastname: Narebor
authors.forename: C
authors.initials: C
authors.lastname: Slingsby
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001123:Argininosuccinate Lyase / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D003196:Computer Graphics; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics; D007908:Lens, Crystalline / Q000737:chemistry*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D014422:Turkeys
chemical_list: D003459:Crystallins; D001123:Argininosuccinate Lyase