L-malate transport and proton symport in vesicles prepared from Pseudomonas putida.
In vesicles from glucose-grown Pseudomonas putida, L-malate is transported by nonspecific physical diffusion. L-Malate also acts as an electron donor and generates a proton motive force (delta p) of 129 mV which is composed of a membrane potential (delta psi) of 60 mV and a delta pH of 69 mV. In contrast, vesicles from succinate-grown cells transport L-malate by a carrier-mediated system with a Km value of 14.3 mM and a Vmax of 313 nmol X mg protein-1 X min-1, generate no delta psi, delta pH, or delta p when L-malate is the electron donor, and produce an extravesicular alkaline pH during the transport of L-malate. A kinetic analysis of this L-malate-induced proton transport gives a Km value of 16 mM and a Vmax of 667 nmol H+ X mg protein-1 X min-1. This corresponds to a H+/L-malate ratio of 2.1. The failure to generate a delta p in these vesicles is considered, therefore, to be consistent with the induction in succinate-grown cells of an electrogenic proton symport L-malate transport system.
D001692:Biological Transport; D002462:Cell Membrane / Q000502:physiology; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008293:Malates / Q000378:metabolism*; D008564:Membrane Potentials; D011522:Protons; D011549:Pseudomonas / Q000378:metabolism*
D008293:Malates; D011522:Protons; C030298:malic acid