title: Characterization of glutamate transport system in hydrophobic protein (H protein) of Bacillus subtilis.
abstract: Hydrophobic protein (H protein) was isolated from membrane fractions of Bacillus subtilis and constituted into artificial membrane vesicles with lipid of B. substilis. Glutamate was accumulated into the vesicle when a Na+ gradient across the membrane was imposed. The maximum effect of Na+ on the transport was achieved at a concentration of about 40 mM, while the apparent Km for Na+ was approximately 8 mM. On the other hand, Km for glutamate in the presence of 50 mM Na+ was about 8 micro M. Increasing the concentration of Na+ resulted in a decrease in Km for glutamate, maximum velocity was not affected. The transport was sensitive to monensin (Na+ ionophore). Glutamate was also accumulated when pH gradient (interior alkaline) across the membrane was imposed or a membrane potential was induced with K+-diffusion potential. The pH gradient-driven glutamate transport was sensitive to carbonylcyanide m-chlorophenylhydrazone and the apparent Km for glutamate was approximately 25 microM. These results indicate that two kinds of glutamate transport system were present in H protein: one is Na+ dependent and the other is H+ dependent.
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D004058:Diffusion; D005971:Glutamates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D005971:Glutamates; D008565:Membrane Proteins; D012965:Sodium Chloride; D011188:Potassium