Structure and Interactions of Gas Vesicles by SSNMR

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DESCRIPTION (provided by applicant): Despite great interest in their remarkable properties, and the considerable range of expertise brought to bear by several groups over many years, only the most general features of the structure of gas vesicles are known. However, recent developments now poise solid state NMR to provide numerous unique probes of the atomic details of the structure of the 7kDa monomer, gvpA, and its assembly into rigid, amyloid-like shells. Preliminary 13C and 15N spectra of uniformly labeled vesicles indicate that a combination of several isotope labeling strategies and an array of multidimensional correlation experiments should allow the full assignment of resonances and the determination of both intra-monomer and inter-monomer structural constraints. Ultimately, this information will allow the complete structure of the gas vesicle shell to be determined. Work will be carried out simultaneously on gas vesicles from the archae Halobacterium salinarum and the cyanobacterium Anabaena flos-aquaea. The parallel efforts will be synergistic because of the strong core homology between the gvpA's of the two species and the different isotope labeling strategies available in the two organisms. The parallel efforts will also be complimentary because of differences in overall vesicle morphology associated with differences in the N- and C-terminal domains of the two gvpA sequences. The role of electrostatics will be explored by identifying the cation displacements and protonation changes that induce vesicle collapse with decreasing pH. The response to salt will also be interesting since H. salinarum is a halophile and A. flos-aquaea is adapted to sweet water. Discovered structural details will shed light on the molecular basis of the morphology and rigidity of the vesicles, the prevention of water condensation within these gas permeable organelles, and the controlled assembly and disassembly of these amyloid-like aggregates.