Cardiolipin membrane domains in prokaryotes and eukaryotes

Abstract

Cardiolipin (CL) plays a key role in dynamic organization of bacterial and mitochondrial membranes. CL forms membrane domains in bacterial cells, and these domains appear to participate in binding and functional regulation of multi-protein complexes involved in diverse cellular functions including cell division, energy metabolism, and membrane transport. Visualization of CL domains in bacterial cells by the fluorescent dye 10-N-nonyl acridine orange is critically reviewed. Possible mechanisms proposed for CL dynamic localization in bacterial cells are discussed. In the mitochondrial membrane CL is involved in organization of multi-subunit oxidative phosphorylation complexes and in their association into higher order supercomplexes. Evidence suggesting a possible role for CL in concert with ATP synthase oligomers in establishing mitochondrial cristae morphology is presented. Hypotheses on CL-dependent dynamic re-organization of the respiratory chain in response to changes in metabolic states and CL dynamic re-localization in mitochondria during the apoptotic response are briefly addressed.

Fig. 1

Staining of living wild type E. coli cells with fluorescent dye NAO revealed dynamic localization of CL enriched membrane domains. (A) Deconvoluted images of an optical section of cells grown in LB media supplemented with 200 nM NAO. Excitation was at 490 nm and emission was at either 528 (left) or 617 (right) nm; bar, 3 μm. (B) E. coli cells stained with NAO growing on a thin layer of LB agar on a microscopy glass slide. Images were taken with time intervals as indicated. Arrows point to CL domains as they appeared in the mid-cell areas of individual cells and further evolved into complete septa structures enriched in CL. (Fluorescent microscopy was performed by Lu Yang and Eugenia Mileykovskaya)

Fig. 2

Altered cristae morphology in mitochondria from S. cerevisiae mutant lacking CL. Purified mitochondria were fixed for electron microscopy by glutaraldehyde followed by further fixation with osmium tetroxide and stained with uranyl acetate. (A) Wild type mitochondria; (B) Δcrd1 mitochondria; (C) onion-like structures in crd1Δ mitochondrial preparation. Bar, 25 nm. (Electron microscopy was performed by Srinivas Mullapudi).