title: Volume changes associated with cytochrome c oxidase-porphyrin cytochrome c equilibrium.
abstract: The binding of a fluorescent derivative of cytochrome c to cytochrome c oxidase has been studied by use of pressure to perturb the equilibrium. delta Vo for the reaction oxidase-porphyrin cytochrome (formula; see text) was small and favored dissociation of the complex. Pressure-induced dissociation is to be expected if the major forces governing the equilibrium are electrostatic in nature. The dependence of log Kd on pressure is not linear but biphasic; high pressures lead to a decrease in Kd and association of the reactants. The latter fact indicates that the net compressibility of the complexes is greater than that of the free reactants, an unexpected result.
mesh_terms: D003576:Electron Transport Complex IV / Q000378:metabolism*; D005454:Fluorescence Polarization; D009994:Osmolar Concentration; D011166:Porphyrins / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011312:Pressure; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
chemical_list: D011166:Porphyrins; C033886:porphyrin c; D011189:Potassium Chloride; D003576:Electron Transport Complex IV