title: X-ray- and neutron-scattering studies of alpha-crystallin and evidence that the target protein sits in the fenestrations of the alpha-crystallin shell.
abstract: OBJECTIVE
  Alpha-crystallin, a ubiquitous molecular chaperone, is found in high concentrations in the lens. Its structure and precise mechanism of action, however, are unknown. The purpose of these experiments was to further the understanding of the chaperone function of alpha-crystallin.
  
  
  METHODS
  X-ray- and neutron-solution-scattering studies were used to measure the radius of gyration of bovine lens alpha-crystallin when complexed with its target protein beta-crystallin in both normal and heavy-water-based solutions. Spectrophotometry was used as a chaperone assay.
  
  
  RESULTS
  The radius of gyration of alpha-crystallin on its own and when mixed with beta-crystallin was 69 +/- 1 A at 35 degrees C and increased with the temperature. In contrast to H2O-buffered solutions, the radius of gyration did not increase significantly in D2O-buffered solutions up to 55 degrees C, and at 70 degrees C was, on average, some 15 to 20 A smaller.
  
  
  CONCLUSIONS
  Bovine lens alpha-crystallin in solution can be modeled as a fenestrated spherical shell of diameter 169 A. At physiological temperatures, a weak interaction between alpha- and beta-crystallin occurs, and beta-crystallin is located in the fenestrations. Deuterium substitution indicates that the superaggregation process is controlled by hydrogen bonding. However, the chaperone process and superaggregation appear not to be linked.
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom. reginijw@cf.ac.uk
authors.forename: Justyn W
authors.initials: JW
authors.lastname: Regini
authors.forename: J Günter
authors.initials: JG
authors.lastname: Grossmann
authors.forename: Peter
authors.initials: P
authors.lastname: Timmins
authors.forename: John J
authors.initials: JJ
authors.lastname: Harding
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Quantock
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Hodson
authors.forename: Gerald F
authors.initials: GF
authors.lastname: Elliott
mesh_terms: D000818:Animals; D002417:Cattle; D018832:Molecular Chaperones / Q000737:chemistry*; D033363:Neutron Diffraction / Q000379:methods*; D011485:Protein Binding; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction / Q000379:methods*; D038201:alpha-Crystallins / Q000737:chemistry*; D038204:beta-Crystallins / Q000737:chemistry
chemical_list: D018832:Molecular Chaperones; D038201:alpha-Crystallins; D038204:beta-Crystallins