6533b85afe1ef96bd12b95b3

RESEARCH PRODUCT

Intracellular accumulation of l-Arg, kinetics of transport, and potassium leak conductance in oocytes from Xenopus laevis expressing hCAT-1, hCAT-2A, and hCAT-2B

Alexander RotmannEllen I. ClossJana F. LiewaldHermann Nawrath

subject

Patch-Clamp TechniquesVoltage clampXenopusBiophysicsArginineBiochemistryMembrane PotentialsXenopus laevisVoltage dependencehCATAnimalsPatch clampCationic Amino Acid Transporter 2y+Cationic Amino Acid Transporter 1Membrane potentialbiologyChemistryBiological TransportTransporterCell Biologybiology.organism_classificationVmaxKMKineticsBiochemistryConductanceOocytesPotassiumBiophysicsAmino Acid Transport Systems BasicEffluxSteady state (chemistry)Intracellular

description

AbstractCationic amino acid transporters play an important role in the intracellular supply of l-Arg and the generation of nitric oxide. Since the transport of l-Arg is voltage-dependent, we aimed at determining the intracellular l-Arg concentration and describing the transport of l-Arg in terms of Michaelis–Menten kinetics, taking into account membrane voltage. The human isoforms of the cationic amino acid transporters, hCAT-1, hCAT-2A, and hCAT-2B, were expressed in oocytes from Xenopus laevis and studied with the voltage clamp technique and in tracer experiments. We found that l-Arg was concentrated intracellularly by all hCAT isoforms and that influx and efflux, in the steady state of exchange, were nearly mirror images. Conductance measurements at symmetric concentrations of l-Arg (inside/outside) allowed us to determine KM and Vmax. The empty transporter of hCAT-2B featured an unexpected potassium conductance, which was inhibited by l-Arg.

yearjournalcountryeditionlanguage
2004-02-06Biochimica et Biophysica Acta (BBA) - Biomembranes
10.1016/j.bbamem.2003.11.009http://dx.doi.org/10.1016/j.bbamem.2003.11.009