Poster abstracts

Poster number 7 submitted by Ian Kleckner

Donut dynamics: NMR studies of the ring-shaped 11-mer trp RNA-binding Attenuation Protein (TRAP)

Ian Kleckner (Department of Biochemistry, The Ohio State University), Craig McElroy (Department of Biochemistry, The Ohio State University), Paul Gollnick (Department of Biological Sciences, SUNY at Buffalo), Philipp Neudecker (Department of Medical Genetics & Microbiology, University of Toronto), Lewis Kay (Department of Medical Genetics & Microbiology, University of Toronto)

Abstract:
The tryptophan biosynthetic pathway in bacilli is regulated by the trp RNA-binding Attenuation Protein (TRAP). TRAP allosterically regulates the expression of the genes in the trp operon through its interactions with the ligand tryptophan, the protein Anti-TRAP (AT) and the nascent mRNA from the trp genes. TRAP forms a radially symmetric ring-shaped undecamer (11-mer) which can bind up to 11 tryptophan molecules. A reciprocal relationship is formed between the local concentration of tryptophan and the expression of the tryptophan biosynthetic genes through interactions with the mRNA. The organism will only express the proteins which synthesize tryptophan if tryptophan is scarce.

Interestingly, evidence suggests that there are only minor structural changes in TRAP upon tryptophan binding. Instead, TRAP's affinity for the mRNA is influenced largely by the dynamics of the TRAP molecule.

Structural and dynamic aspects of TRAP have been characterized by measuring amide N and Hn temperature coefficients, H/D exchange, methyl relaxation dispersion and tryptophan-induced chemical shift perturbations in the side chain methyl groups of TRAP.

References:
McElroy, C., Manfredo, A., Wendt, A., Gollnick, P., and Foster, M. (2002) TROSY-NMR studies of the 91kDa TRAP protein reveal allosteric control of a gene regulatory protein by ligand-altered flexibility, J. Mol. Biol. 323, 463-473.

Mcelroy, C., Manfredo, A., Gollnick, P., Foster, M. (2006) Thermodynamics of Tryptophan-Mediated Activation of the trp RNA-Binding Attenuation Protein, Biochem. 45, 7844-7853.

Keywords: TRAP, NMR, dynamics