Abstract
Overexpression of AtBI-1 (Arabidopsis thaliana Bax inhibitor-1) could suppress the Bax-induced cell death in yeast and Arabidopsis, and the H2O2- or SA-induced cell death in tobacco BY-2 cells. AtBI-1 protein possesses seven putative transmembrane helixes, of which the C-terminal 14 amino acids are seemed to locate in cytosol. The deletion of the 14 amino acids resulted in lose of the ability to suppress Bax or H2O2-induced cell death with the maintenance of ER localization. Although the substitution of C-terminal charged amino acids conserved in animals and plants did not affect to the ability to suppress the Bax-induced cell death in yeast, a mutant protein lacking coiled-coil structure failed to suppress cell death, indicating that the C-terminal structure is essential. Furthermore, the coiled-coil structure was also required for interaction between calmodulin and AtBI-1, suggesting the involvement of calcium ion in suppression of cell death by AtBI-1.
