PMID: 7298576Nov 1, 1981

Ammonium and methylammonium transport by the nitrogen-fixing bacterium Azotobacter vinelandii

Journal of Bacteriology
J K Gordon, R A Moore


Azotobacter vinelandii, grown with NH4+ as nitrogen source, was shown to possess an active transport system which can take up NH4+ against a concentration gradient of 58-fold. The properties of the NH4+ uptake system were investigated with the NH4+ analog CH3NH3+. The use of this analog was justified on the basis of the conclusion that the uptake of NH4+ and CH3NH3 involves a common binding site, as shown by the competitive inhibition of CH3NH3+ uptake by NH4+ (Ki approximately 3 microM). A Lineweaver-Burk plot for CH3NH3+ uptake revealed a biphasic curve, suggesting the existence of two CH3NH3+ (NH4+) uptake systems with apparent Km's for CH3NH3+ equal to 61 microM and 661 microM. The uptake of CH3NH3+ was inhibited by arsenate, as well as by cyanide or carbonyl cyanide-m-chlorophenyl hydrazone, indicating that phosphate bond energy is required.

Related Concepts

Pyroarsenic acid
Methylamine, monosodium salt
Quaternary Ammonium Compounds
Carbonyl Cyanide m-Chlorophenyl Hydrazone
Potassium Cyanide (K(C(15)N))

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