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.
The insect V-ATPase, a plasma membrane proton pump energizing secondary active transport: molecular analysis of electrogenic potassium transport in the tobacco hornworm midgut.
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H Wieczorek; The insect V-ATPase, a plasma membrane proton pump energizing secondary active transport: molecular analysis of electrogenic potassium transport in the tobacco hornworm midgut.. J Exp Biol 1 November 1992; 172 (1): 335–343. doi: https://doi.org/10.1242/jeb.172.1.335
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