2bb2
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X-RAY ANALYSIS OF BETA B2-CRYSTALLIN AND EVOLUTION OF OLIGOMERIC LENS PROTEINS
OverviewOverview
The beta, gamma-crystallins form a class of homologous proteins in the eye lens. Each gamma-crystallin comprises four topologically equivalent, Greek key motifs; pairs of motifs are organized around a local dyad to give domains and two similar domains are in turn related by a further local dyad. Sequence comparisons and model building predicted that hetero-oligomeric beta-crystallins also had internally quadruplicated subunits, but with extensions at the N and C termini, indicating that beta, gamma-crystallins evolved in two duplication steps from an ancestral protein folded as a Greek key. We report here the X-ray analysis at 2.1 A resolution of beta B2-crystallin homodimer which shows that the connecting peptide is extended and the two domains separated in a way quite unlike gamma-crystallin. Domain interactions analogous to those within monomeric gamma-crystallin are intermolecular and related by a crystallographic dyad in the beta B2-crystallin dimer. This shows how oligomers can evolve by conserving an interface rather than connectivity. A further interaction between dimers suggests a model for more complex aggregates of beta-crystallin in the lens.
About this StructureAbout this Structure
2BB2 is a Single protein structure of sequence from Bos taurus with as ligand. Full crystallographic information is available from OCA.
ReferenceReference
X-ray analysis of beta B2-crystallin and evolution of oligomeric lens proteins., Bax B, Lapatto R, Nalini V, Driessen H, Lindley PF, Mahadevan D, Blundell TL, Slingsby C, Nature. 1990 Oct 25;347(6295):776-80. PMID:2234050
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