HIGH-AFFINITY TRANSPORT OF HISTIDINE AND METHIONINE ACROSS LEPTINOTARSA-DECEMLINEATA MIDGUT BRUSH-BORDER MEMBRANE

High affinity transport of histidine and methionine across the midgut brush border membrane of Leptinotarsa decemlineata was characterized u sing brush border membrane vesicles (BBMV). Histidine transport was no t stimulated by sodium or potassium. Methionine transport was stimulat ed by monovalent cations. Sodium was more stimulatory than cesium or l ithium. Divalent cations, Mg2+ and Ca2+, were not stimulatory, and the re was no effect of Cl-. Methionine transport was most strongly inhibi ted by 100-fold excess concentrations of cysteine, serine and leucine. L. decemlineata midgut has both ion-dependent and ion-independent tra nsporters that differ from those in other insects and mammals. CryIIIA toxin did not inhibit uptake of methionine or histidine into BBMV.