How shape leads to disease
Ribosomal, transfer and messenger RNAs all play critical roles in protein synthesis. Transfer RNAs act as adaptor molecules since they contain the triplet anticodon code for a particular amino acid. Enzymes known as aminoacyl-tRNA synthetases attach an amino acid to the transfer RNA (tRNA) and these so-called charged tRNAs are then used to translate the genetic code from messenger RNA into protein. The three-dimensional shape of the tRNA is important for the synthetases to be able to charge the tRNA.
Changes or mutations in a number of human mitochondrial tRNA genes have been associated with a wide variety of human diseases. Mitochondria are the energy producing machines in mammalian cells and they encode a complete set of tRNAs, sufficient to support mitochondrial protein synthesis.
To understand how these changes lead to cellular dysfunctions, Paul Schimmel and coworkers at the Scripps Research Institute in La Jolla, California, USA studied mutations associated with a particular disease known as opthalmoplegia. They found that mutant tRNAs impaired the ability of the synthetase to add the amino acid [Nature Structural Biology (Vol. 7, No. 10, October 2000)]. These tRNAs contained mismatched base pairs in different parts of the molecule that could be 'fixed' by replacement with a properly matched base pair. Based on these studies they suggest that the instability of the overall shape of the tRNA molecule is responsible for the disease. It will be interesting to understand in more detail how reductions in mitochondrial energy (ATP) production in nerve, muscle or other tissues contribute to various degenerative diseases.
Dr. Paul Schimmel
The Skaggs Institute for Chemical Biology,
The Scripps Research Institute
10550 North Torrey Pines Road
La Jolla, California 92037
Tel: 858 784 8970
Fax: 858 784 8990
(C) Nature Structural Biology press release.
Message posted by: Trevor M. D'Souza