1blb
From Proteopedia
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'''CLOSE PACKING OF AN OLIGOMERIC EYE LENS BETA-CRYSTALLIN INDUCES LOSS OF SYMMETRY AND ORDERING OF SEQUENCE EXTENSIONS''' | '''CLOSE PACKING OF AN OLIGOMERIC EYE LENS BETA-CRYSTALLIN INDUCES LOSS OF SYMMETRY AND ORDERING OF SEQUENCE EXTENSIONS''' | ||
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[[Category: Nalini, V.]] | [[Category: Nalini, V.]] | ||
[[Category: Slingsby, C.]] | [[Category: Slingsby, C.]] | ||
| - | [[Category: | + | [[Category: Eye lens protein]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:39:54 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 08:39, 2 May 2008
CLOSE PACKING OF AN OLIGOMERIC EYE LENS BETA-CRYSTALLIN INDUCES LOSS OF SYMMETRY AND ORDERING OF SEQUENCE EXTENSIONS
Overview
beta-Crystallins are oligomeric eye lens proteins that are related to monomeric gamma-crystallins. The main sequence difference between the two families is the presence of sequence extensions in the beta-crystallins. A major question concerns the role that these extensions play in mediating interactions at the high protein concentrations found in the lens. The predominant beta-crystallin polypeptide, beta B2, can be crystallized in two different space groups, I222 and C222. The I222 crystal structure revealed that the protein packed as a tetramer with perfect 222 symmetry but that the extensions were disordered. The X-ray structure of the C222 lattice of beta B2 has now been refined at 3.3 A, the structure analysed and compared with the I222 lattice. The protein is also a tetramer with 222 symmetry in the C222 lattice but differs in that parts of the N-terminal extensions have been visualized. In the asymmetric unit of the C222 lattice there are four subunits, each comprising a single polypeptide chain, in which certain flexible loops in the N-terminal domains and the N-terminal extensions have various conformations. The tetramers in the C222 lattice are more tightly packed than in the I222 form. Analysis of the tetramer contacts shows that the sites of interaction break the 222 symmetry of the tetramers. The N-terminal extensions play a major role in directing interactions between tetramers. One of the N-terminal extensions interacts with a hydrophobic patch on the N-terminal domain of another tetramer. These crystallographic observations obtained over a physiological concentration range indicate how, in beta-crystallin oligomers, the N-terminal extensions of beta B2 can switch from interacting with water to interacting with protein depending on their relative concentrations. This could be useful in maintaining a gradient of refractive index.
About this Structure
1BLB is a Single protein structure of sequence from Bos taurus. Full crystallographic information is available from OCA.
Reference
Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions., Nalini V, Bax B, Driessen H, Moss DS, Lindley PF, Slingsby C, J Mol Biol. 1994 Mar 4;236(4):1250-8. PMID:8120900 Page seeded by OCA on Fri May 2 11:39:54 2008
