My primary research interest is chloroplast biogenesis. Specifically, work in my laboratory centers around the transport and assembly of cytoplasmically synthesized chloroplast proteins. We have used the precursor of the small subunit (pS) of ribulose-1,5-bisphosphate carboxylase/oxygenase as a model substrate for the E. coli chaperonin GroEL. Construction of a number of deletion and site-specific mutations in pS allowed us to identify the GroEL binding site and to measure the affinity of the chaperonin for the substrate. Our attention has now turned to cytoplasmic chaperones involved in the transport of precursor proteins to the chloroplast. By using pS or other precursors of chloroplast proteins as affinity ligands, we have identified several polypeptides which preferentially bind chloroplast precursor proteins. We currently are attempting to identify and characterize these cytoplasmic chaperones.
We also have studied the chloroplast carbonic anhydrase. We have sequenced the gene from Arabidopsis thaliana, and have sequenced cDNAs from a number of plants. In addition, using site-directed mutagenesis and biophysical methods, we have identified the zinc ligands in the spinach enzyme. Work on this project has now shifted to utilization of transgenic plants for studies of the effects of under-expression of carbonic anhydrase on chloroplast metabolism as well as investigation of cis-acting sequences in the promoter which regulate expression of the protein.
Floyd, Z. E. and S. G. Bartlett. 1995. Nucleotide Sequence of a cDNA Encoding Eukaryotic Initiation Factor 5 (Accession No. L47221) In Bean. Plant Physiol. Plant Gene Register PGR95-092.
Bracey, M. H. and S. G. Bartlett. 1995. Sequence Of a cDNA Encoding Carbonic Anhydrase From Barley. Plant Physiol.108:433-434.
Bracey, M. H., J. Christiansen, P. Tovar, S. P. Cramer and S. G. Bartlett. 1994. Spinach Carbonic Anhydrase: Investigation of the Zinc-Binding Ligands by Site-Directed Mutagenesis, Elemental Analysis, and EXAFS. Biochemistry 33:13126-13131.
Kim, H. J., M. H. Bracey, and S. G. Bartlett. 1994. Nucleotide Sequence of a Gene Encoding Carbonic Anhydrase in Arabidopsis thaliana. Plant Physiol. 105:449.
Dessauer, C. W. and S. G. Bartlett. 1994. Identification of a Chaperonin Binding Site in a Chloroplast Precursor Protein. J. Biol. Chem. 269:19766-19776.