Scientists at the University of Freiburg have discovered a new mechanism that is of central significance for the architecture and functioning of mitochondria, known as the power plants of the cell. With the help of chemical reactions that take place on their inner membranes, these organelles convert food into energy for the metabolism and growth of the cell. The inner mitochondrial membrane features a characteristic architecture that is essential for its role as an energy transducer. Errors in the structure of the mitochondria can lead to serious illnesses in humans, particularly illnesses affecting the muscles and nerves.
The inner mitochondrial membrane forms tubular invaginations known as cristae, and these delicate generators of the power plants are surrounded by an outer mitochondrial membrane. The composition of this microstructure, which is identical in all organisms, from unicellular life forms to human beings, has remained a mystery until now. In a joint research project between the Priority Program SFB 746, the Cluster of Excellence Centre for Biological Signalling Studies (BIOSS), and the Spemann Graduate School of Biology and Medicine (SGBM), a team of scientists in Freiburg led by Dr. Martin van der Laan and Prof. Bettina Warscheid has discovered an enormous molecular machine composed of six different membrane proteins that is necessary for attaching the cristae to the envelope of the mitochondria in the unicellular model organism baker's yeast.
The study, now published in the journal Developmental Cell, demonstrates that defects in this protein complex lead to the detachment of the cristae, causing severe growth disturbances in the cell.
In cooperation with Prof. Agnieszka Chacinska from the International Institute for Molecular and Cell Biology in Warsaw, Poland, the research team was also able to demonstrate that the central component of this fascinating protein machinery is not only essential for the inner architecture of the cellular power plants but also forms molecular contact points between the two mitochondrial membranes. These membrane bridges facilitate the transport of new proteins produced outside into the mitochondria.
With their discovery of a supporting pillar of the architecture of mitochondria, the researchers succeeded in solving a much discussed problem in cellular biology and making a significant contribution to our understanding of the structure and functioning of the cellular power plants. The findings could prove to be helpful for explaining numerous mechanisms of illnesses which involve a change in the structure of the mitochondria.
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