M. Thamotharan et Ga. Ahearn, DIPEPTIDE TRANSPORT BY CRUSTACEAN HEPATOPANCREATIC BRUSH-BORDER MEMBRANE-VESICLES, Journal of Experimental Biology, 199(3), 1996, pp. 635-641
Epithelial brush-border membrane vesicles (BBMVs) of lobster (Homarus
americanus) hepatopancreas were formed by a Mg2+ precipitation techniq
ue, In these BBMVs, [C-14]glycylsarcosine ([C-14]Gly-Sar) uptake was s
timulated by a transmembrane proton gradient, transmembrane K+ diffusi
on potential (inside negative) stimulated [C-14]Gly-Sar uptake above t
hat observed with short-circuited vesicles, while an inwardly directed
Na+ gradient had no stimulatory effect on peptide uptake. [C-14]Gly-S
ar influx (over 10 s) occurred by a low-affinity, saturable, proton-gr
adient-dependent carrier system (K-t=5.90+/-0.13 mmoll(-1), J(max)=466
2+/-487 pmol mg(-1) protein 10 s(-1); mean +/- S.E.M., N=3). This carr
ier exhibited a high-affinity proton binding site (K-H=235+/-25 nmoll(
-1); pK=6.6) and an apparent 1H(+):1Gly-Sar transport stoichiometry. I
nflux of 0.1 mmoll(-1) [C-14]Gly-Sar into lobster hepatopancreatic BBM
Vs was significantly (P<0.01) cis-inhibited by 10 mmoll(-1) diethylpyr
ocarbonate and by a variety of other dipeptides (10 mmoll(-1)), sugges
ting a broad transport specificity, These observations strongly sugges
t that transport of peptides into crustacean hepatopancreas is proton-
gradient-dependent and electrogenic, qualitatively resembling the pept
ide transport paradigm proposed for fish and mammals.