V-ATPases are ubiquitous proton pumps found in eukaryotes, and are important in regulating the pH of cell compartments and in creating membrane potentials, The V-ATPase creates a proton gradient that is used as an energy source for the transport of other ions. The 16-kDa proteolipid is the proton-translocating subunit c of V-ATPases. Using PCR methods, we have cloned the fire ant 16-kDa subunit c, providing the first molecular characterization of this protein in a social insect. Northern blot analysis revealed three possible different transcripts. The presence of V-ATPases in ant Malpighian tubules had been previously demonstrated, where they provide the proton gradient necessary for the excretion of other ions and the formation of primary urine, The 16-kDa proteolipid is highly conserved among insects, and in ants may be important to the critical processes of diuresis and olfaction as a key component of the V-ATPase. (C) 2001 Wiley-Liss, Inc.