ABC TRANSPORTER · Biochemical characterization of the Arabidopsis ABC transporter AtABCB14 and exploring why it exhibits an import activity

The genome of Arabidopsis thaliana is predicted to encode 129 ABC proteins, which are involved in many physiological processes such as transport of metabolites, toxic substance, and regulation of stomatal movement (Martinoia et al., 2001; Rea, 2007). The ABC protein AtABCB14 is implicated in the regulation of stomatal movement by transporting malate into guard cells (Lee et al. 2008). This is only the second plant ABC transporter shown to act as an importer and no animal counterpart has been shown to exhibit an import activity. The goal of this project is to carry out a detailed analysis of AtABCB14. To do this I will i) Characterize the kinetics and the substrate activities of AtABCB14; ii) Use site-directed mutagenesis and substrate-dependent ATP-hydrolysis to investigate whether the import activity is ATP-dependent; iii) Carry out experiments to find structural determinants which are responsible for the import activity of this ABC transporter. The identification of the biochemical properties and the import mechanism of AtABCB14 will be helpful to understand why only plants have ABC transporters exhibiting import activity. Furthermore, the identification of factors responsible for the import activity may provide important information to the medical field and cancer research.