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Updated: Aug 8, 2026

Glutamine Flux Imaging Using Genetically Encoded Sensors
Published on: July 31, 2014
Glutamate transport in Rhodobacter sphaeroides is mediated by a novel binding protein-dependent secondary transport
M H Jacobs1, T van der Heide, A J Driessen
1Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
Abstract:
Growth of a glutamate transport-deficient mutant of Rhodobacter sphaeroides on glutamate as sole carbon and nitrogen source can be restored by the addition of millimolar amounts of Na+. Uptake of glutamate (Kt of 0.2 microM) by the mutant strictly requires Na+ (K(m) of 25 mM) and is inhibited by ionophores that collapse the proton motive force (pmf). The activity is osmotic-shock-sensitive and can be restored in spheroplasts by the addition of osmotic shock fluid. Transport of glutamate is also observed in membrane vesicles when Na+, a proton motive force, and purified glutamate binding protein are present. Both transport and binding is highly specific for glutamate. The Na(+)-dependent glutamate transporter of Rb. sphaeroides is an example of a secondary transport system that requires a periplasmic binding protein and may define a new family of bacterial transport proteins.
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