Glutamate transport in Rhodobacter sphaeroides is mediated by a novel binding protein-dependent secondary transport system.
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.
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
M H
MH
Jacobs
T
T
van der Heide
A J
AJ
Driessen
W N
WN
Konings
D001224:Aspartic Acid / Q000378:metabolism; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D009154:Mutation; D009550:Nigericin / Q000494:pharmacology; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
D007476:Ionophores; D005973:Glutamine; D014634:Valinomycin; D001224:Aspartic Acid; D018698:Glutamic Acid; D014638:Vanadates; D012964:Sodium; D009550:Nigericin