The alphaA-crystallin R116C mutant has a higher affinity for forming heteroaggregates with alphaB-crystallin

Biochemistry. 2002 Jan 8;41(1):297-305. doi: 10.1021/bi011010v.


An autosomal dominant congenital cataract in humans is associated with mutation of Arg-116 to Cys in alphaA-crystallin (alphaA-R116C). The chaperone activity and biophysical properties of reconstituted alpha-crystallin from different proportions of wild-type alphaB-crystallin (alphaB-wt) and alphaA-R116C-crystallin were studied by gel permeation chromatography, SDS-polyacrylamide gel electrophoresis, and fluorescence and circular dichroism spectroscopy and compared with those of reconstituted alpha-crystallin from alphaB-wt and wild-type alphaA-crystallin (alphaA-wt). The reconstituted alpha-crystallin containing alphaA-R116C and alphaB-wt had a higher molecular mass, a higher thermal sensitivity to exposition of Trp side chains, fewer available hydrophobic surfaces, and lower chaperone activity than the alpha-crystallin containing alphaA-wt and alphaB-wt. The secondary structure exhibited very small changes, whereas the tertiary structure was distinctly different for alpha-crystallin formed from alphaA-R116C and alphaB-wt. Most importantly, subunit exchange studies by fluorescence resonance energy transfer showed that alphaA-R116C forms heteroaggregates faster than alphaA-wt with alphaB-wt, and the reconstituted alpha-crystallins were true heteroaggregates of two interacting subunits. These findings suggest that the molecular basis for the congenital cataract with the alphaA-R116C mutation is the formation of highly oligomerized heteroaggregates of alpha-crystallin with modified structure. However, contrary to the earlier conclusions based on the studies of homoaggregates, the loss in chaperone activity of the heteroaggregates having alphaA-R116C does not appear to be large enough to become the main factor in initiating cataract development in the affected individuals.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anilino Naphthalenesulfonates / pharmacology
  • Animals
  • Binding Sites
  • Circular Dichroism
  • Crystallins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / enzymology
  • Fluorescent Dyes / pharmacology
  • Kinetics
  • Molecular Chaperones / metabolism
  • Mutation
  • Protein Binding / drug effects
  • Protein Conformation / drug effects
  • Protein Subunits
  • Rats
  • Temperature
  • Time Factors


  • Anilino Naphthalenesulfonates
  • Crystallins
  • Fluorescent Dyes
  • Molecular Chaperones
  • Protein Subunits
  • 1-anilino-8-naphthalenesulfonate