2BB2

X-RAY ANALYSIS OF BETA B2-CRYSTALLIN AND EVOLUTION OF OLIGOMERIC LENS PROTEINS

Summary for 2BB2

• Entry DOI: 10.2210/pdb2bb2/pdb
• Descriptor: BETA B2-CRYSTALLIN, BETA-MERCAPTOETHANOL (3 entities in total)
• Functional Keywords: eye lens protein
• Biological source: Bos taurus (cattle)
• Total number of polymer chains: 1
• Total formula weight: 20897.27

Authors

Bax, B.,Lapatto, R.,Nalini, V.,Driessen, H.,Lindley, P.F.,Mahadevan, D.,Blundell, T.L.,Slingsby, C. (deposition date: 1992-09-21, release date: 1993-10-31, Last modification date: 2024-06-05)

Primary citation

Bax, B.,Lapatto, R.,Nalini, V.,Driessen, H.,Lindley, P.F.,Mahadevan, D.,Blundell, T.L.,Slingsby, C.
X-ray analysis of beta B2-crystallin and evolution of oligomeric lens proteins.
Nature, 347:776-780, 1990

PubMed 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.

PubMed: 2234050
DOI: 10.1038/347776a0

Experimental method

X-RAY DIFFRACTION (2.1 Å)