1. Department of Cell Biology, University of Geneva, 1211 Geneva 4, Switzerland.
2. School of Pharmaceutical Sciences, University of Geneva, 1211 Geneva 4, Switzerland.
3. Institute of Molecular Systems Biology, 8093 Zurich, Switzerland.
4. Zellbiologie, Universität Bayreuth, 95440 Bayreuth, Germany.
5. Mitochondria Biology Unit, Medical Research Council, Cambridge CB2 0XY, UK.