We have conducted the preliminary solid-state NMR studies of the phosphorus contained in a gas vesicles protein (GVP). Gas vacuoles (GV) are inert, hollow, gas-filled structures, which provide buoyancy to the prokaryotic species in which they are present. The wall of GV is constructed solely from a protein, and more than two homologous proteins with molecular weights of 8.4 kDa and 382 kDa are found in the GV isolated from Halobacterium halobium. About 0.2 mmol very tightly bound phosphate per mg of protein were discovered as well. The 31P CP/MAS spectra of lyophilized GVP show the presence of at least two components. The downfield component (at 5.9 ppm) is relatively narrow, and the upfield one (at w3 ppm) is considerably broader and mobile as indicated from the Bloch decay spectra. The chemical shift tensor elements of the narrow component were determined at both room and low temperature (-80~C). A change of 8 ppm was observed in d11 (most downfield tensor element), which has been shown to correlate with the length of the longest P-O bond in phosphates. Our future work includes a study of phosphate esters with different amino acids which will help us assign the 31P resonances observed in GVP. Our ultimate goal is to determine the structure of the phosphate linkage to the protein. Experiments on GVP isolated via slightly different procedure and intact gas vacuoles are also planned.
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