Office: SSB 6144
Phone: (604) 291-4355
Current Research Program:
We are interested in the biosynthesis and regulation of plant and bacterial chlorophylls. We are currently cloning and overexpressing some of the genes encoding enzymes of bacteriochlorophyll biosynthesis (bch genes). The overexpressed gene products are then examined for enzyme activity in order to confirm the assignment of bch genes to particular enzymes. In the first completed project, the bchH gene (which actually encodes one of three subunits of the magnesium chelatase enzyme complex) has been cloned and overexpressed. The overexpressed BchH protein by itself has been shown to activate the next enzyme in the metabolic sequence, a methyltransferase. The BchH protein may, therefore, act to link the magnesium chelatase complex to (and in the process activate) the membrane-bound methyltransferase. We have also now completed the cloning and overexpression of the bchF gene, and are currently examining the gene product for its proposed enzyme activity.
The pufQ gene, although not encoding an enzyme, is required for optimum biosynthesis of bacteriochlorophyll in Rhodobacter capsulatus. The gene has recently been cloned and overexpressed in E. coli as a fusion protein in which the PufQ protein was linked to a maltose-binding protein through a specific protease recognition sequence. Antibodies generated against the purified fusion protein were used in immunoblot analysis to identify the PufQ protein in photosynthetic membranes of R. capsulatus. The PufQ protein was released from the fusion protein by proteolysis, purified, and reconstituted into phospholipid vesicles. Binding studies indicated that it had some affinity for an intermediate of bacteriochlorophyll synthesis, and might be acting as a carrier protein of magnesium tetrapyrrole intermediates. However, more recent work has indicated that it acts to stimulate tetrapyrrole synthesis much earlier in the pathway (before the production of magnesium tetrapyrroles). We have currently prepared a pufQ- mutant and have isolated suppressor mutants which are able to form bacteriochlorophyll and grow photosynthetically in the absence of the pufQ gene. The identity of these suppressor mutations is currently being investigated.
Last updated 11/15/2000