PDBsum entry: 1blb

Eye lens protein

PDB id: 1blb

Contents

Protein chains

185 a.a. *

* Residue conservation analysis

PDB id:

1blb

Name:

Eye lens protein

Title:

Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions

Structure:

Beta b2-crystallin. Chain: a, b, c, d. Engineered: yes

Source:

Bos taurus. Cattle. Organism_taxid: 9913. Tissue: lens

Biol. unit:

Tetramer (from PQS)

Resolution:

3.30Å R-factor: not given

Authors:

V.Nalini,B.Bax,H.Driessen,D.S.Moss,P.F.Lindley,C.Slingsby

Key ref:

V.Nalini et al. (1994). Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions. J Mol Biol, 236, 1250-1258. PubMed id: 8120900 DOI: 10.1016/0022-2836(94)90025-6

Date:

22-Dec-93 Release date: 20-Dec-94

Protein chains

P02522  (CRBB2_BOVIN) -  Beta-crystallin B2

Seq: 205 a.a.

Struc: 185 a.a.

 Gene Ontology (GO) functional annotation 

• Biological process: camera-type eye development (2 terms)
• Biochemical function: structural constituent of eye lens (3 terms)

DOI no: 10.1016/0022-2836(94)90025-6

J Mol Biol 236:1250-1258 (1994)

PubMed id: 8120900

Close packing of an oligomeric eye lens beta-crystallin induces loss of symmetry and ordering of sequence extensions.

V.Nalini, B.Bax, H.Driessen, D.S.Moss, P.F.Lindley, C.Slingsby.

ABSTRACT

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.

Selected figure(s)

Figure 5.
Figure 5. A4n expanded view of the 70's loop in the cxgion here tptrarnrs in the (.`22:! lattice are stacked in ,he : irrction. Tetramers are shown as either continuous r broken ines. a) The site of interactin of 4 CDC*D* -terminal domains n proximity to- a non-crystallo- graphic- axis. The iew is t.he same as in Figure4(a). nterac%ions involving side-rhains from the C subunit can be ithin a tetramer or between different tetramers. (b) The equivalent region involving ABA*B* tet,ramers.

Figure 6.
Figure 6. The interactions nvolving K-terminal extensions. A CD dimer is shown as a continuous line in \vhic*h the K-terminal arm of the ' subunit is interacting with the N-terminal domain of the B suunit of an AB dimrr on the uIjI,et

The above figures are reprinted by permission from Elsevier: J Mol Biol (1994, 236, 1250-1258) copyright 1994.

Figures were selected by an automated process.