Characterization of arginine transport in Helicobacter pylori.
BACKGROUND
The amino acid L-arginine is an essential requirement for growth of Helicobacter pylori. Several physiological roles of this amino acid have been identified in the bacterium, but very little is known about the transport of L-arginine and of other amino acids into H. pylori.


METHODS
Radioactive tracer techniques using L-(U-14C) arginine and the centrifugation through oil method were employed to measure the kinetic parameters, temperature dependence, substrate specificity, and effects of analogues and inhibitors on L-arginine transport.


RESULTS
The transport of arginine at millimolar concentrations was saturable with a Km of 2.4+/ 0.3 mM and Vmax of 1.3+/-0.2 pmole min(-1) (microl cell water)(-1) or 31+/-3 nmole per minute (mg protein)(-1) at 20 degrees C, depended on temperature between 4 and 40 degrees C, and was susceptible to inhibitors. These characteristics suggested the presence of one or more arginine carriers. The substrate specificity of the transport system was studied by measuring the effects of L-arginine analogues and amino acids on the rates of transport of L-arginine. The absence of inhibition in competition experiments with L-lysine and L-ornithine indicated that the transport system was not of the Lysine-Arginine-Ornithine or Arginine-Ornithine types. The presence of different monovalent cations did not affect the transport rates. Several properties of L-arginine transport were elucidated by investigating the effects of potential inhibitors.


CONCLUSIONS
The results provided evidence that the transport of L-arginine into H. pylori cells was carrier-mediated transport with the driving force supplied by the chemical gradient of the amino acid.
Mendz
George L
GL
School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW 2052, Australia.
Burns
Brendan P
BP
D026905:Amino Acid Transport Systems / Q000037:antagonists & inhibitors / Q000502:physiology*; D001120:Arginine / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001667:Binding, Competitive; D001692:Biological Transport; D002414:Cations, Monovalent / Q000378:metabolism; D016480:Helicobacter pylori / Q000378:metabolism*; D007700:Kinetics; D008239:Lysine / Q000378:metabolism; D009952:Ornithine / Q000378:metabolism; D011849:Radioactive Tracers; D013696:Temperature
D026905:Amino Acid Transport Systems; D002414:Cations, Monovalent; D011849:Radioactive Tracers; D001120:Arginine; D009952:Ornithine; D008239:Lysine