抄録
Bax inhibitor-1(BI-1), an endoplasmic reticulum membrane protein, is widely conserved cell death suppressor in plants and animals. The overexpression of Arabidopsis BI-1 (AtBI-1) suppresses the oxidative stress-induced plant cell death. To investigate the molecular mechanism of BI-1-medited cell death suppression, we identified BI-1 interactors from Arabidopsis. Calmodulin (CaM), a calcium signaling mediator, is a first identified BI-1 binding protein. The C-terminal region of AtBI-1 interacted with CaM, and such interaction was essential for the cell death suppression activity of AtBI-1. In addition, cytochrome b5 (Cb5), an electron transfer protein localized mainly in the ER membrane, was isolated as an interactor of AtBI-1. On the other hand, functional screening of yeast gene disruptant demonstrated that AtBI-1 required sphingolipid fatty acid 2-hydroxylase (FAH) for its cell death suppression activity. The BiFC and FRET analysis demonstrated interaction of AtCb5 and AtFAHs in plant cells, suggesting thatAtBI-1 interacts with AtFAHs via Cb5 in plant cells. These data indicates that lipid modification by BI-1 may be important to protect plant cells from oxidative stresses.
