Proton Magnetic Resonance Spectroscopy of Promitochondrial Membranes from Yeast Grown Under Different Regimes of Lipid Supplementation

Promitochondrial membranes, prepared from Saccharomyces cerevisiae grown anaerobically under different conditions of lipid supplementation, have been examined by PMR spectroscopy. Promitochondria from cells cultured anaerobically in media containing both unsaturated fatty acid and sterol supplements, or containing unsaturated fatty acid alone, yield high resolution spectra similar to those which are characteristic of aerobic mitochondria. By contrast, promitochondrial membranes from cells grown only with sterol supplementation in order to deplete unsaturated fatty acid and total phospholipid content of the organelles, yielded PMR spectra which were very substantially broadened. These spectra are similar to those obtained with rat liver mitochondria. PMR spectra of promitochondria from each cell type dispersed in trifluoroacetic acid, or of extracted lipids or residual proteins similarly dispersed, were different only in detail. It appears, therefore, that in the native state membranes of unsaturated fatty acid-depleted promitochondria are structurally different from promitochondria of the other two cell types. The difference may be a consequence of altered lipid-to-protein ratios, and thus of changes in the extent of lipid domain formation in the membranes of these organelles.