J. Biol. Chem., Vol. 255, Issue 11, 5224-5229, Jun, 1980
Energy-linked quinacrine fluorescence changes in submitochondrial particles from skeletal muscle mitochondria. Evidence for intramembrane H+ transfer as a primary reaction of energy coupling
BT Storey, DM Scott and C Lee
Submitochondrial particles obtained from skeletal muscle are open membrane
fragments which show energy coupling yet cannot sustain transmembrane ion
gradients. An energy-linked decrease in fluorescence emission of the
fluorescent probe quinacrine is observed with skeletal muscle particles
which is enhanced by the anion SCN-. This is essentially the same reaction
observed with beef heart submitochondrial particles, in which the reaction
is known to be a monitor of intramembrane H+ transfer. The results with
skeletal muscle particles show that this intramembrane H+ transfer occurs
in the absence of any electrochemical potential across the membrane.
Further, it occurs independently of the direction of H+ exchange with the
suspendingly medium, since energization of skeletal muscle submitochondrial
particles is known to give H+ efflux into the medium, while energization of
beef heart particles gives H+ uptake from the medium. We conclude that a
primary reaction of energy coupling is intramembrane H+ transfer linked to
electron transport but shielded from the suspending medium. Movements of H+
between membrane and medium are secondary reactions derived from the
primary one, possibly linked by a series of intramembrane conformational
changes comprising a sequential membrane Bohr effect.
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