Molecular analysis of system N suggests novel physiological roles in nitrogen metabolism and synaptic transmission.
Chaudhry, FA Reimer, RJ Krizaj, D Barber, D Storm-Mathisen, J Copenhagen, DR Edwards, RH
||Chaudhry FA, etal., Cell 1999 Dec 23;99(7):769-80.
||(View Article at PubMed) PMID:10619430
The amino acid glutamine has a central role in nitrogen metabolism. Although the molecular mechanisms responsible for its transport across cell membranes remain poorly understood, classical amino acid transport system N appears particularly important. Using intracellular pH measurements, we have now identified an orphan protein related to a vesicular neurotransmitter transporter as system N. Functional analysis shows that this protein (SN1) involves H+ exchange as well as Na+ cotransport and, under physiological conditions, mediates glutamine efflux as well as uptake. Together with the pattern of SN1 expression, these unusual properties suggest novel physiological roles for system N in nitrogen metabolism and synaptic transmission.
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