Vacuolar function is essential to the regulation of cytosolic calcium levels. Calcium-binding proteins unique to the vacuolar membrane have been identified. The immediate goal of this project is to purify and characterize these proteins in terms of affinity, capacity, and cation selectivity. Polyclonal antibodies will be used to study the tissue-specific expression patterns of these proteins, particularly with regard to the process of vacuolation and biogenesis of the vacuole membrane system. Antibody will further serve to identify cDNA clones in expression libraries encoding these proteins. %%% Plant cells contain large membrane-enclosed compartments, which serve a number of biochemical and structural functions for the plant cell. Some of these are relatively "universal" functions associated generally with lysosome-type compartments; others are unique for plants. Accordingly, the vacuole has an essential role in growth and development. It is remarkable that few vacuolar membrane activities have been examined and fewer still have been identified and examined at the molecular level. There is not yet a clear understanding of either the origins of this organelle or the means by which vacuolar membrane proteins are continuously replenished. This study will contribute to an understanding of the molecular basis for the role of the vacuole in conferring to higher plants the ability to respond to its environment and carry out the normal processes of growth and development.
