A Quantitative Analysis of Super-Stoichiometric H+ Ejection and Ca2+ Uptake in Respiring Rat Liver Mitochondria

摘要: Abstract Experiments described in this paper provide an explanation for super-stoichiometry of respiration-dependent uptake Ca2+ and ejection H+ by mitochondria, i.e. Ca2+/2e- ratios greatly exceeding 2.0 per site correspondingly increased H+/2e- when the medium is devoid phosphate. In rat liver mitochondria evoked concentrations excess 60 to 80 ng-ions mg protein, otherwise normal reaction 120 mm KCl, pH 7.2. Super-stoichiometric caused a distinctly different process than stimulation oxygen consumption. Kinetic analysis shows that Ca2+-stimulated under conditions yielding biphasic. It consists (1) large early burst release, 1400 min, which ratio may be infinitely high; (2) slow phase stoichiometric with electron transport. Simultaneously, there binding, exceed 1000 again very high ratio, respiration. are thus due rapid energy-dependent binding superimposed on slower, The extra require finite preceding period State 4 transport, presumably energization. Some 40 50 bound up ejected protein optimal conditions. Similar results observed Sr2+ uptake, but Mn2+ yields only phase. Since superstoichiometry occurs absence permeant anions mersalyl present prevent cycling mitochondrial phosphate, it concluded fast involve specific membrane-binding sites. postulated energization membrane causes changes affinity these sites, leading decreased