Gas vesicles across kingdoms: a comparative solid state NMR study

The buoyancy organelles of aquatic microorganisms have to meet stringent specifications: allowing gases to equilibrate freely across the proteinaceous shell, preventing the condensation of water vapor inside the hollow cavity, and resisting collapse under hydrostatic pressures that vary with column depth. These properties are provided by the 7–8 kDa gas vesicle protein A (GvpA), repeats of which form all but small, specialized portions of the shell. Magic angle spinning NMR is uniquely capable of providing high resolution information on the fold and assembly of GvpA. Here we compare results for the gas vesicles of the haloarchae Halobacterium salinarum with those obtained previously for the cyanobacterium Anabaena flos-aquae. The data suggest that the two organisms follow similar strategies for avoiding water condensation. On the other hand, in its relatively shallow habitat, H. salinarum is able to avoid collapse with a less costly GvpA fold than is adopted by A. flos-aquae.