Linked Life Data

8120900

Source:http://linkedlifedata.com/resource/pubmed/id/8120900

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1994-4-7
pubmed:abstractText
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.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
4
pubmed:volume
236
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1250-8
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1994
pubmed:articleTitle
Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions.
pubmed:affiliation
Laboratory of Molecular Biology, Birkbeck College, London University, UK.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't