structural and functional characterization of plant calmodulins

Abstract

Unlike animals, plants express several CaM isoforms. A unique variant of calmodulin which bears a C-terminal prenylation site is present in some plant cells such as Oryza sativa and Petunia hybrida. In this thesis I demonstrated that the tail adopts a partial helical structure and that the tail interacts with different regions of the protein in the presence and absence of calcium. Altogether it seems that the tail represents a new regulatory mechanism that plants can utilize to control calcium signalling. Another interesting aspect of calcium signalling are the plant-specific calcium-ATPases and their interactions with calmodulin. In this thesis the structure of soybean calmodulin isoform 4 (sCaM4) in complex with ACA2 and ACA8, which belong to two different groups of calcium-ATPases, were examined. Altogether it seems that the CaM-binding domain of different calcium-ATPases with different locations in the cell have unique structural characteristics, which leads to distinct regulation by sCaM4.