Analysis of the data on titration of native and peroxynitrite modified αA- and αB-crystallins by Cu-ions.

The interaction of αA- and αB-crystallins with Cu ion modulates their structure and chaperone-like activity which is important for lens transparency. Theoretical analysis of the dependences of fluorescence intensity of native αA- and αB-crystallins and αA- and αB-crystallins modified by peroxynitrite on concentration of Cu ions has been carried out. It has been shown that one subunit of native αA-crystallin contains two equivalent Cu-binding sites. The microscopic dissociation constant for Cu-αA-crystallin complex ( ) was found to be equal to 9.7 µM. For peroxynitrite modified αA-crystallin the value is equal to 17 µM. One subunit of native αB-crystallin contains two non-equivalent Cu-binding sites. The corresponding microscopic dissociation constants for Cu-αB-crystallin complexes ( and ) were found to be equal to 0.94 and 36 µM. For peroxynitrite modified αB-crystallin the and values are equal to 4.3 and 70 µM, respectively.