title: Second system for potassium transport in Streptococcus faecalis.
abstract: It has been reported that the accumulation of K+ by Streptococcus faecalis is mediated by a transport system which required both ATP and the proton motive force (Bakker and Harold, J. Biol. Chem. 255:433-440, 1980). My results indicate that S. faecalis has a second transport system for K+. The features of this system are as follows: (i) the system is driven by ATP (or a derivative of ATP) and does not require the proton motive force; (ii) the system is normally absent in the wild-type strain but can be derepressed by lowering rhe intracellular concentration of K+; (iii) the pH optimum of this system is about 8.5, and no detectable K+ is accumulated at pH values below 6.5; and (iv) the rate of Rb+ accumulation by this system is very low. These properties are quite different from those of the transport system described by Bakker and Harold. Therefore, I propose that S. faecalis has two K+ transport systems.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D013293:Enterococcus faecalis / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009154:Mutation; D011188:Potassium / Q000378:metabolism*; D011522:Protons
chemical_list: D011522:Protons; D004024:Dicyclohexylcarbodiimide; D000255:Adenosine Triphosphate; D011188:Potassium