Low and high affinity amino acid H+-cotransporters for cellular import of neutral and charged amino acids.

Amides and acidic amino acids represent the major long distance transport forms of organic nitrogen. Six amino acid permeases (AAPs) from Arabidopsis mediating transport of a wide spectrum of amino acids were isolated. AAPs are distantly related to plasma membrane amino acid transport systems N and A and to vesicular transporters such as VGAT from mammals.

A high affinity fungal nitrate carrier with two transport mechanisms.

We have expressed the CRNA high affinity nitrate transporter from Emericella (Aspergillus) nidulans in Xenopus oocytes and used electrophysiology to study its properties. This method was used because there are no convenient radiolabeled substrates for the transporter. Oocytes injected with crnA mRNA showed nitrate-, nitrite-, and chlorite-dependent currents.

Role of Cl- in electrogenic Na+-coupled cotransporters GAT1 and SGLT1.

We have investigated the functional role of Cl(-) in the human Na(+)/Cl(-)/gamma-aminobutyric acid (GABA) and Na(+)/glucose cotransporters (GAT1 and SGLT1, respectively) expressed in Xenopus laevis oocytes. Substrate-evoked steady-state inward currents were examined in the presence and absence of external Cl(-). Replacement of Cl(-) by gluconate or 2-(N-morpholino)ethanesulfonic acid decreased the apparent affinity of GAT1 and SGLT1 for Na(+) and the organic substrate.

Molecular cloning, chromosomal localization, tissue distribution, and functional expression of the human pancreatic sodium bicarbonate cotransporter.

We report the cloning, sequence analysis, tissue distribution, functional expression, and chromosomal localization of the human pancreatic sodium bicarbonate cotransport protein (pancreatic NBC (pNBC)). The transporter was identified by searching the human expressed sequence tag data base. An I.