Abstract：
: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.
journal_name
Naturejournal_title
Natureauthors
Bax B,Lapatto R,Nalini V,Driessen H,Lindley PF,Mahadevan D,Blundell TL,Slingsby Cdoi
10.1038/347776a0subject
Has Abstractpub_date
1990-10-25 00:00:00pages
776-80issue
6295eissn
0028-0836issn
1476-4687journal_volume
347pub_type
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