The insect V-ATPase, a plasma membrane proton pump energizing secondary active transport: molecular analysis of electrogenic potassium transport in the tobacco hornworm midgut.
Goblet cell apical membranes in the larval midgut of Manduca sexta are the site of active and electrogenic K+ secretion. They possess a vacuolar-type ATPase which, in its immunopurified form, consists of at least nine polypeptides. cDNAs for the A and B subunits screened by monoclonal antibodies to the A subunit of the Manduca V-ATPase or by hybridisation with a cDNA probe for a plant V-ATPase B subunit have been cloned and sequenced. There is a high degree of identity to the sequences of the respective subunits of other V-ATPases. The M. sexta plasma membrane V-ATPase is an electrogenic proton pump which energizes, by the electrical component of the proton-motive force, electrogenic K+/nH+ antiport, resulting in net electrogenic K+ secretion. Since the midgut lacks a Na+/K(+)-ATPase, all solute fluxes in this epithelium seem to be energized by the V-ATPase. Thus, the midgut provides an alternative to the classical concept of animal plasma membrane energization by the Na(+)-motive force generated by the Na+/K(+)-ATPase.
Wieczorek
H
H
Zoologisches Institut der Universität, München, Germany.
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism; D017136:Ion Transport; D009036:Moths / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D017494:Proton Pumps / Q000502:physiology; D025262:Vacuolar Proton-Translocating ATPases
D017494:Proton Pumps; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases; D011188:Potassium