Related Experiment Video
Updated: Feb 7, 2026
Protein Modifications: Protein Kinases and Phosphatases
Molecular analysis of system N suggests novel physiological roles in nitrogen metabolism and synaptic transmission
F A Chaudhry1, R J Reimer, D Krizaj
1Department of Neurology, UCSF School of Medicine, San Francisco, California 94143-0435, USA.
Abstract:
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.
Related Concept Videos
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Regulated Protein Degradation
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein....
Co-activators and Co-repressors
Activation Energy
Activation and Inactivation of G Proteins