The midgut plasma membrane V-ATPase from larval Manduca sexta, the tobacco hornworm, is the sole energizer of any epithelial ion transport in this tissue and is responsible for the alkalinization of the gut lumen up to a pH of more than 11. This mini-review deals with those topics of research on this enzyme which may have contributed or are expected to contribute novel and general aspects to the field of V-ATPases. Topics dealt with include novel subunits or the quaternary structure of the V1 complex, as well as the regulation of the enzyme's function by reversible dissociation of the V1 from the V0 complexes and by genetic control on the transcriptional and posttranscriptional level.