Identification of 1,1′-bi(4-anilino)naphthalene-5,5′-disulfonic acid binding sequences in α-crystallin

The hydrophobic binding sites in alpha-crystallin were evaluated using fluorescent probes 1,1'-bi(4-anilino)naphthalenesulfonic acid (bis-ANS), 8-anilino-1-naphthalene sulfonate; (ANS), and 1-azidonaphthalene 5-sulfonate (1,5-AZNS). The photolysis of bis-ANS-alpha-crystallin complex resulted in incorporation of the probe to both alpha A- and alpha B-subnnits, Prior binding of denatured alcohol dehydrogenase to alpha-crystallin significantly decreased the photoincorporation of bis-ANS to alpha-crystallin. Localization of bis-ANS incorporated into alpha A-cryskallin resulted in the identification of residues QSLFR and HFSPEDLTVK as the fluorophore binding regions, In alpha B-crystallin, sequences DRFSVNLNVK and VLGDVIEVHGK were found to be the Ibis-ANS binding regions, Of the bis-ANS binding sequences, HFSPEDLTVK of alpha-A-crystallin and DRFSVNLNVK and VLGDVIEVHGK of alpha B-crystallin were earlier identified as part of the sequences involved in their interaction with target proteins during the molecular chaperone-like action. The hydrophobic probe, 1,5-AZNS, also interacted with both subunits of alpha-crystallin. Localization of 1,5-AZNS binding site in alpha B-crystallin lead to the identification of HFSPEEK sequence as the interacting site in this subunit of alpha-crystallin, Glycated alpha-crystallin displayed decreased ANS fluorescence and loss of chaperone-like function, suggesting the involvement of glycation site as well as ANS binding site ire chaperone-like activity display.