Research Overview

The energy-producing organelles of eukaryotic cells, chloroplasts and mitochondria possess a circular DNA and the necessary apparatus for replication of this DNA and for transcription and translation of the genes it encodes. Photosynthetic eukaryotes are unique in their ability to assemble both types of subcellular organelle within the same cell.

In my laboratory, we are studying two specific aspects of organellar biogenesis in green plants: a) the regulation of expression of nuclear genes encoding chloroplast and mitochondrial protein synthesis factors, and b) the mechanisms by which cytoplasmically synthesized proteins are differentially targeted to chloroplasts and mitochondria.

We are also studying structure-function relationships in protein synthesis factor EF-G. This protein catalyzes the translocation step of the elongation cycle of protein synthesis in bacteria and eukaryotic organelles, and is a member of the superfarnily of GTPases. Other members of the GTPase superfarnily have been implicated in a wide variety of cellular functions, including signal transduction, protein secretion, and control of developmental pathways. We are using site-directed and random mutagenesis to identify amino acids that are required for EF-G activity, hoping to better understand its mechanism of action.

Publications

B. Chen, A.R. Kubelik, S. Mohr and C.A. Breitenberger (1996)  Cloning and characterization of the Neurospora crassa cyt-5 gene: A nuclear-codedmitochondrial RNA polymerase with a poly- glutamine repeat  J. Biol. Chem. 271: 6537-6544.

P.L. Welcsh, D.R. Johnson, Y. Zhang and C.A. Breitenberger (1994)  Synechocystis sp. PCC 6803 fusB gene, located outside of the str operon, encodes a polypeptide related to protein synthesis factor EF-G. Plant Mol. Biol. 25, 735-738.

M.S. Akkaya, P.L. Welcsh, M.A. Wolfe, B.K. Duerr, W.J. Becktel and C.A. Breitenberger (1994) Purification and N-terminal sequence analysis of pea chloroplast protein synthesis factor EF-G. Arch. Biochem. Biophys. 308, 109-117.