Relationship of potassium ion transport and ATP synthesis in pea cotyledon mitochondria

Abstract

Simultaneous monitoring of ATP synthesis and K+ movements across pea mitochondrial membranes revealed information about the competition of the two processes for mitochondrial energy. In the presence of valinomycin and at low extramitochondrial K+ concentration, ADP could be phosphorylated rapidly. This occurred with a decrease in net potassium ion uptake. At higher external K+ concentrations respiratory energy was unavailable for ATP synthesis and only a portion of added ADP could be phosphorylated within a reasonable time. Magnesium ions were shown to have an inhibitor effect on the K+ uptake, and stimulated a greater rate of ATP synthesis. When valinomycin and ADP were added simultaneously so that phosphorylation of the ADP and enhancement of K+ uptake could complete for mitochondrial energy, K+ uptake was preferred over ATP synthesis.

PROTON MOTIVE FORCE INHIBITORS ARE DETRIMENTAL TO METHICILLIN-RESISTANTSTAPHYLOCOCCUS AUREUSPERSISTER CELLS

“…The chemicals in the library inhibit different mechanisms of the mitochondrial ETC system 51,52,61,62,[66][67][68][53][54][55][56][57][58][59][60] . The ETC is evolutionarily conserved across species 63 , which may explain the observed high hit rate achieved by screening a small chemical library.…”

“…Each chemical was tested at four different concentrations in the wells of a 96-well plate. These chemicals included complex I inhibitors (rotenone and pyridaben), complex II inhibitors (malonate and carboxin), complex III inhibitors (antimycin A and myxothiazol), uncouplers [trifluoromethoxy carbonylcyanide phenylhydrazone (FCCP) and 2,4-dinitrophenol], ionophores (valinomycin and calcium chloride), and other chemicals (gossypol, nordihydroguaiaretic acid, polymyxin B, amitriptyline, meclizine, berberine, alexidine, phenformin, diclofenac, celastrol, trifluoperazine, and papaverine) that directly or indirectly inhibit the ETC of mitochondria 51,52,61,62,[53][54][55][56][57][58][59][60] . Although this library was specifically designed for mammalian cells, we reasoned that some of the chemicals might be effective for bacteria as the ETC is evolutionarily conserved 63 .…”