Abstract
Bax inhibitor-1 (BI-1) is a widely conserved ER membrane protein known as cell-death suppressor. Overexpression of AtBI-1 (Arabidopsis BI-1) suppresses the H2O2-, SA- or elicitor-induced cell death in plant cells. To investigate the function of AtBI-1 in detail, isolation of interacting factors of AtBI-1 was performed by screening of Arabidopsis cDNA library. Using yeast split-ubiquitin system, we found AtCb5 (Arabidopsis cytochrome b5) as a candidate of such factor. Cb5 is known to be a ubiquitous electron transport protein whose function is formation or modification of fatty acid. Furthermore, AtBI-1 was supposed to interact with AtFAH (Arabidopsis fatty acid hydroxylase) via AtCb5. Arabidopsispossesses several homologs of AtCb5, of which such interaction was found in AtCb5s localized in ER and mitochondria. In particular, AtBI-1 interacted with the cytosolic N-terminal region of AtCb5 containing the catalytic heme-binding domain. Possible role of such proteins in lipid metabolic pathway will be presented.
