Gas vesicles are small, hollow, gas filled protein structures that are found in several microbial planktonic microorganisms. They allow the positioning of the organism at the favorable depth for growth. GvpA type proteins form the essential core of the structure (By similarity). It is not clear if the 2 type A proteins in this organism are functionally redundant (PubMed:9573198). When the gvp locus is expressed in E.coli gas vesicles are made. Not essential for gas vesicle formation in E.coli. Belongs to the gas vesicle protein type A family.