Structural changes in bovine lens crystallins induced by ascorbate, metal, and oxygen

Ascorbate, Fe³⁺, or Cu²⁺ and oxygen induced the oxidation of bovine lens crystallins. The modifications mimicked those that occur in the lens with aging. The modifications included the formation of nondisulfide crosslinks in α- and β_H-crystallin and the cleavage of α-, β_H-, and the low molecular weight crystallin fractions. In all three fractions, there was a loss of the more basic protein species and an increase in the more acidic species. Nontryptophan fluorescence with emission spectra between 400 and 500 nm was produced in β_H-crystallin. Cu²⁺ was less effective than Fe³⁺ in catalyzing the modification of β_H-and γ-crystallin. Both metal ions were equally effective in catalyzing the modification of α-crystallin.