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Biomedical subjects

P Mitchell

Publications and source records attributed to P Mitchell.

At least 523 records · Page 29Linked to original sources
PubMed1974

Proton/sodium ion antiport in Escherichia coli.

In anaerobic suspensions of Escherichia coli, after H(+) ions have been translocated outwards across the plasma membrane by a respiratory pulse, re-equilibration is catalysed by Na(+). The sudden addition of a Na(+) salt causes the effective outward translocation of H(+) by an electroneutral process. We conclude that the plasma membrane of E. coli contains a Na(+)/H(+) antiport system that normally translocates Na(+) outwards under the influence of an inwardly directed H(+)-activity gradient.

Biological Transport, Active↗
PubMed1973

The proton-translocating nicotinamide-adenine dinucleotide (phosphate) transhydrogenase of rat liver mitochondria.

1. The NAD(P) transhydrogenase activity of the soluble fraction of sonicated rat liver mitochondrial preparations was greater than the NAD-linked isocitrate dehydrogenase activity, and the NAD-linked and NADP-linked isocitrate dehydrogenase activities were not additive. The NAD-linked isocitrate dehydrogenase activity was destroyed by an endogenous autolytic system or by added nucleotide pyrophosphatase, and was restored by a catalytic amount of NADP. 2. We concluded that the isocitrate dehydrogenase of rat liver mitochondria was exclusively NADP-specific, and that the oxoglutarate/isocitrate couple could therefore be used unequivocally as redox reactant for NADP in experiments designed to operate only the NAD(P) transhydrogenase (or loop 0) segment of the respiratory chain in intact mitochondria. 3. During oxidation of isocitrate by acetoacetate in intact, anaerobic, mitochondria via the rhein-sensitive, but rotenone- and arsenite-insensitive, NAD(P) transhydrogenase, measurements of the rates of carbonyl cyanide p-trifluoromethoxyphenylhydrazone-sensitive and carbonyl cyanide p-trifluoromethoxyphenylhydrazone-insensitive pH change in the presence of various oxoglutarate/isocitrate concentration ratios gave an -->H(+)/2e(-) quotient of 1.94+/-0.12 for outward proton translocation by the NAD(P) transhydrogenase. 4. Measurements with a K(+)-sensitive electrode confirmed that the electrogenicity of the NAD(P) transhydrogenase reaction corresponded to the translocation of one positive charge per acid equivalent. 5. Sluggish reversal of the NAD(P) transhydrogenase reaction resulted in a significant inward proton translocation. 6. The possibility that isocitrate might normally be oxidized via loop 0 at a redox potential of -450mV, or even more negative, is discussed, and implies that a P/O quotient of 4 for isocitrate oxidation might be expected.

Acetoacetates↗
PubMed1973

Stoicheiometry of lactose-H+ symport across the plasma membrane of Escherichia coli.

The rate of [(14)C]lactose inflow into anaerobic, non-metabolizing, Escherichia coli has been correlated with the rate of the simultaneous effective inflow of H(+). It is shown that the initial rates of the two transport processes are essentially the same, and it is concluded that the two processes are strictly coupled with a 1:1 stoicheiometry.

Anaerobiosis↗