Monday, 26 September, 2011
Structure of a molecular copy machine
How mitochondrial genes are transcribed
The mitochondria are the cell’s power stations. In animal cells, they supply energy in usable form by converting nutrients into the universal energy currency of the cell, adenosine triphosphate (ATP). Mitochondria possess their own DNA, and are inherited via the maternal line. The mitochondrial DNA codes for a small number of proteins that are essential for energy production in the organelle. The first step in the decoding of this genetic information is the synthesis, or transcription, of RNA copies of the DNA by the enzyme mitochondrial RNA polymerase. The RNA molecules are then used to program protein synthesis. However, exactly how the mitochondrial RNA polymerase actually works has not been clear, as its structure was unknown – until now. Biochemist Professor Patrick Cramer, Director of the Gene Center at LMU, in collaboration with Professor Dmitry Temiakov of the University of Medicine and Dentistry of New Jersey (USA), has now determined the architecture of this molecular copy machine. “With the help of a synchrotron as a source of radiation and using the method of X-ray diffraction, we were able to determine the first three-dimensional structure of a human polymerase, the mitochondrial RNA polymerase, in atomic detail,” Cramer explains.