X-ray analysis of βB2-crystallin and evolution of oligomeric lens proteins

B. Bax, R. Lapatto, V. Nalini, H. Driessen, P. F. Lindley, D. Mahadevan, T. L. Blundell, C. Slingsby

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233 Scopus citations

Abstract

THE β, γ-crystallins form a class of homologous proteins in the eye lens. Each γ-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 dyad1-4. Sequence comparisons and model building predicted that hetero-oligomeric β-crystallins also had internally quadruplicated subunits, but with extensions at the N and C termini, indicating that β, γ-crystallins evolved in two duplication steps from an ancestral protein folded as a Greek key5-7. We report here the X-ray analysis at 2.1 Å resolution of βB2-crystall in homodimer which shows that the connecting peptide is extended and the two domains separated in a way quite unlike γ-crystallin. Domain interactions analogous to those within monomeric γ-crystallin are intermolecular and related by a crystallographic dyad in the βB2-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 β-crystallin in the lens.

Original languageEnglish (US)
Pages (from-to)776-780
Number of pages5
JournalNature
Volume347
Issue number6295
DOIs
StatePublished - 1990

ASJC Scopus subject areas

  • General

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