The structure of avian eye lens delta-crystallin reveals a new fold for a superfamily of oligomeric enzymes

Nat Struct Biol. 1994 Oct;1(10):724-34. doi: 10.1038/nsb1094-724.


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, 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Argininosuccinate Lyase / chemistry
  • Argininosuccinate Lyase / genetics
  • Binding Sites
  • Computer Graphics
  • Crystallins / chemistry*
  • Crystallins / genetics
  • Lens, Crystalline / chemistry*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Structure, Secondary
  • Sequence Homology, Amino Acid
  • Turkeys


  • Crystallins
  • Argininosuccinate Lyase