Specificity of alphaA-crystallin binding to destabilized mutants of betaB1-crystallin.
To elucidate the structural and energetic basis of attractive protein interactions in the aging lens, we investigated the binding of destabilized mutants of betaB1-crystallin to the lens chaperones, alpha-crystallins. We show that the mutations enhance the binding affinity to alphaA- but not alphaB-crystallin at physiological temperatures. Complex formation disrupts the dimer interface of betaB1-crystallin consistent with the binding of a monomer. Binding isotherms obtained at increasing concentrations of betaB1-crystallin deviate from a classic binding equilibrium and display cooperative-like behavior. In the context of betaB1-crystallin unfolding equilibrium, these characteristics are reflective of the concentration-dependent change in the population of a dimeric intermediate that has low affinity to alphaA-crystallin. In the lens, where alpha-crystallin binding sites are not regenerated, this may represent an added mechanism to maintain lens transparency.
McHaourab
Hassane S
HS
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA. hassane.mchaourab@vanderbilt.edu
Kumar
M Satish
MS
Koteiche
Hanane A
HA
D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D013816:Thermodynamics; D038202:alpha-Crystallin A Chain / Q000378:metabolism*; D038206:beta-Crystallin B Chain / Q000737:chemistry* / Q000378:metabolism*
D050505:Mutant Proteins; D038202:alpha-Crystallin A Chain; D038206:beta-Crystallin B Chain