Lab Research Focus
There are two major research projects in the Turnbough laboratory. The first project is to determine the structure and function of the exosporium of spores of Bacillus anthracis, the causative agent of anthrax. The exosporium, the outermost permeability barrier of the spore, is a bipartite structure consisting of a paracrystalline basal layer and an external hair-like nap. The filaments of the nap are formed by trimers of the collagen-like glycoprotein BclA, while the basal layer contains approximately 20 different proteins. Most basal layer proteins are structural elements that undergo posttranslational modifications necessary for stable exosporium assembly. These modifications, as well as posttranslational modifications of BclA, are currently being actively studied. Of particular interest is the spontaneous formation of isopeptide bonds that cross-link many exosporium proteins. The second project focuses on mechanisms of gene regulation in Escherichia coli that involve reiterative transcription and/or transcription start site switching. Reiterative transcription is the repetitive addition of a nucleotide to the 3' end of a nascent transcript due to slippage between the transcript and DNA template. Start site switching is the selection of alternative start sites at a single promoter, which results in the synthesis of transcripts with different potentials for translation. Previous studies have described control mechanisms in which reiterative transcription during initiation and/or start site switching regulate(s) the expression of several operons involved in pyrimidine biosynthesis and salvage. Recently, additional operons have been shown to use reiterative transcription and/or start site switching to regulate their expression by mechanisms unlike those previously described. These new mechanisms are presently being elucidated. In addition, studies are in progress to define the mechanisms of reiterative transcription and start site switching and the factors that modulate the extent of these reactions.
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