Cytoplasmic organelles: What DNA cannot tell us
Schatz, G.
Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
The sequencing of entire genomes has given new urgency to the old question of whether the information laid down in a cell‘s DNA completely describes a eukaryotic cell. Insights gained from studying the evolution and biogenesis of mitochondria and chloroplasts suggest that the answer to this question is “no“. For example, the assembly of these organelles requires complex machineries for importing proteins made on cytosolic ribosomes to the different intra-organellar locations. These machineries are composed of dozens of proteins in the cytosol, the organellar membranes, and the inner spaces of the organelles and require a precise intracellular and transmembrane topology in order to work. Current evidence strongly suggests that these machineries cannot self-assemble without a pre-existing copy of the machinery: assembly is template-dependent. For this reason, every essential protein of the yeast mitochondrial protein import system is essential for cell viability under all conditions. The same will probably be found for chloroplasts. It may even be true for organelles lacking their own genome, such as peroxisomes, the Golgi apparatus, and the endoplasmic reticulum.
The template function of membranes has been postulated before, but we now have the information to understand this function in molecular detail. It is a major challenge to learn what fraction of our genetic heritage is encoded in the structure of our cellular organelles.
Schatz; G. and Dobberstein, B. (1996): Common principles of protein translocation across membranes. Science 271, 1519-1526.
Schatz, G. (1996): The protein import system of mitochondria. J. Biol. Chem. 271, 31763-31766.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Sunday, April 5 |
11:30 am |