Regulation of mitochondrial protein transport: Tim23 as a link to the calcium-signalling network in the cell

• Applicant: Dr. Fatima Chigri, Ph.D.
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 176913070

Many metabolic processes essential for plant viability take place in mitochondria. To ensure that function of this organelle is carefully balanced in accordance with requirements of the cell, mitochondria are tightly integrated into diverse regulatory networks. We recently described an influence of calcium/calmodulin on protein import into plant mitochondria at the level of the TIM23 and TIM22 mediated translocation on the inner membrane. Preliminary studies indicate, that Tim23 itself, the central pore of the TIM23 complex, could be a target for the calcium signal. The Arabidopsis genome encodes three paralogues of Tim23, named atTim23-1, atTim23-2 and atTim23-3 and preliminary studies have shown the ability of atTim23-2 to bind calmodulin, thereby suggesting the protein as a potential mediator for calcium/calmodulin regulation of TIM23 translocation. Aim of the project is the functional characterization of all three atTim23’s in order to elucidate their mode of action with a special focus on a link to calcium regulation of mitochondrial protein import. Furthermore, additional components of the calcium regulon of mitochondria will be elucidated, such as the mediator of calcium regulation of TIM22 translocation and the respective sensors of the calcium signals. The overall aim of the proposal is to understand the molecular basis of calcium regulation of mitochondrial protein transport to facilitate future studies on the adaptation of this process to different environmental or developmental cues.

• DFG Programme: Research Grants