Our research is directed at understanding the role phospholipids play in organization of membrane proteins into macro-molecular machines. This assumes membrane lateral heterogeneity and formation of a network of membrane lipid-protein domains. We are using two models, the highly specialized membrane of yeast mitochondria, containing enzymes of the oxidative phosphorylation system, and the multifunctional bacterial membrane of Escherichia coli. The bacterial model is employed to study interaction of phospholipids with the cytoskeletal proteins of the bacterial division machinery. We investigate the mutual influence of amphitropic cell division proteins, which undergo dynamic oligomerization on the membrane surface, and membrane phospholipids, in the formation of dynamic lipid-protein domains. Our hypothesis is that the domains enriched by the anionic phospholipid cardiolipin (CL) play an important role in the bacterial cell division process. We also participate in a collaborative study to explore the action of a number of antimicrobial agents, the primary target of which is anionic phospholipids. Using the yeast model we investigate the role of CL in organization of electron transfer enzymes of the respiratory chain into supra-molecular structures termed as supercomplexes. Although the existence of respiratory supercomplexes is now generally accepted, the factors that regulate their formation and function are not well understood. Earlier, using a yeast model system, we discovered a direct correlation between CL levels and levels of respiratory supercomplexes thus showing that CL played a central role in supercomplex formation. Subsequently, a significant amount of data have been accumulated by different groups demonstrating that in many diseases, including Barth syndrome, neurodegenerative diseases, heart failure, and cancer, the defects in respiratory supercomplex formation are associated with reduced levels of CL or alterations in the landscape of CL species. Currently we focus on understanding the precise molecular mechanism for the CL-dependent formation and stabilization of the supercomplexes. Our approach combines biochemical, structural and computational studies. We have performed the first in vitro reconstitution of the yeast supercomplex composed of Complex III and two Complexes IV from the purified individual complexes in CL containing liposomes. In our recent structural studies a 3D density map of the yeast respiratory supercomplex composed of Complex III and two Complexes IV was obtained by electron cryo-microscopy and image processing. The structure shows gaps between the transmembrane-localized interfaces of individual complexes consistent with the large excess of CL in the supercomplex over tightly bound CL in the structure of individual respiratory complexes. We hypothesize that non-integral CL molecules play an important role in supercomplex formation and may be involved in regulation of its stability under metabolic conditions where CL levels fluctuate.