title: Discrimination between Rb+ and K+ by Escherichia coli.
abstract: 1. The K+ requirment of Escherichia coli is only partially fulfilled by Rb+. The molar growth yield on Rb+ was about 5% of that on K+ and the growth rate in Rb+-supplemented media is lower thatn in K+ influx by any of the four K+ transport systems of E. coli. The high-affinity Kdp system (Km = 2 micron) is poorly traced by 86Rb+. It discriminates against a 86Rb+ tracer at least 1000-fold. The two moderate affinity systems, the high-rate TrkA system (Km = 1.5 mM) and the moderate rate TrkD system (Km = 0.5 mM), discriminate against a 86Rb+ tracer by approximately 10-fold and 25-fold, respectively. 86Rb+ is preferred by the low-rate TrkF system and overestimates its K+ influx by 40%.
mesh_terms: D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D011868:Radioisotopes; D012413:Rubidium / Q000378:metabolism*
chemical_list: D011868:Radioisotopes; D012413:Rubidium; D011188:Potassium