Not Accepting Doctoral Students
Protein Synthesis of Mammalian Mitochondria
Ph.D., Massachusetts Institue of Technology (1973); B.S., The University of Rochester (1969)
Mammalian mitochondrial protein synthesis: Mitochondria play a crucial role in the metabolism of mammalian cells. Through the process of oxidative phosphorylation, mitochondria generate about 90% of the energy used in the cells of higher organisms. Mitochondria contain their own genome and are capable of transcription and translation. The genetic code is altered in this organelle; the transfer RNAs and mRNAs have numerous unusual features and the ribosomes show significant differences from ribosomes of other translational systems.
Our present objective is to combine the techniques of biochemistry and molecular biology to develop an understanding of the mechanism of protein synthesis in mammalian mitochondria. We have purified a number of factors required for protein synthesis in this system and large amounts of these proteins have been prepared by over-expression in E. coli for use in mechanistic studies. Structure/function studies are being carried out in combination site-directed mutagenesis, molecular modeling, biochemical and biophysical characterization. We are developing a detailed picture of protein-protein and protein-RNA interactions central to mitochondrial translation. Defects in mitochondrial ribosomes, tRNAs or auxiliary factors are associated with serious, often fatal, human genetic diseases. We are exploring the molecular consequences to these defects in the hopes of developing strategies for their treatment.
All of the proteins synthesized by mammalian mitochondrial ribosomes are components of the electron transport chain and ATP synthase used to generate energy for the cell. They are all membrane proteins that function as parts of large oligomeric complexes. The ribosome associates with the inner membrane of the mitochondrion allowing the synthesis of these proteins and their insertion into the membrane to be coordinated. The protein Oxa1L is an integral membrane protein that interacts with the ribosome helping anchor it to the membrane. Oxa1L is part of a large oligomeric complex in the membrane. We are identifying the other components of this complex using proteomics. Additional peripheral membrane proteins mediate the interaction of the ribosome with the membrane. Affinity purification followed by proteomics is being used to determine the identity of these ribosome receptors on the membrane.