Abstract
AtBI-1 (Arabidopsis thaliana Bax Inhibitor-1) is considered to be associated with the resistance against ROS (reactive oxygen species) stresses such as H2O2- or salicylic acid. AtBI-1 is known to localize in ER membranes, and has seven transmembrane domains. The AtBI-1 lacking the C-terminal 14 amino acid residues lost the activity as a cell death suppressor. Several studies have suggested that cellular calcium levels played an important role in determination of the cells' sensitivity to various cell death-inducing stresses. Using yeast split-ubiquitin system, we discovered that AtBI-1 interacted with barley calmodulin (CaM) protein. Furthermore, we demonstrated that the C-terminal region of AtBI-1 could directly interact with calmodulin. Namely, Arabidopsis has 16 CaM genes (AtCaMs) in its genome. The overlay assay showed that at least two CaMs (AtCaM7 and AtCaM6) were able to interact with C-terminal 14 amino acids. The biological meaning of the interaction between CaM and AtBI-1 will be discussed.
