KChIP3: a binding protein for Taiwan banded krait beta-bungarotoxin.

Using B1 chain of beta-bungarotoxin (beta-Bgt) as bait in yeast two-hybrid screen, we found that KChIP3 was a binding protein of B1 chain. Thus, protein-protein interaction between beta-Bgt and KChIP3 is investigated in the present study. Pull-down assay showed that recombinant KChIP3 proteins were associated with beta-Bgt as well as B1 chain, whereas the inability of KChIPs 1, 2 and 4 to bind with beta-Bgt was observed. Although Ca2+ was not a crucial factor essential for the binding of KChIP3 with beta-Bgt and B1 chain, their interaction could be enhanced by the addition of Ca2+. Alternatively, the association of A1 chain of beta-Bgt with KChIP3 was marginally detected. The dissociation constant of beta-Bgt with KChIP3 were 12.2 and 6.08 microM in the absence and presence of 2mM Ca2+, respectively. Moreover, native KChIP3 from rat brain was to be isolated by beta-Bgt-Sepharose. These observations indicate that KChIP3 is a binding protein of beta-Bgt. In view of the multiple functions of KChIP3 in neuronal cells, the interaction of KChIP3 with beta-Bgt may represent an event for the manifestation of the biological activities of beta-Bgt.