Biological membranes—especially those of eukaryotes—are composed of several types of lipids. Cardiolipin is one such lipid that has both a unique molecular structure and distinctive physical properties. It is typically found within mitochondrial membranes, where it is known to modulate membrane structure and dynamics. Due to the central role that mitochondria play as the cellular powerhouse, their unique membrane composition and structure are critical to facilitate a variety of important biochemical processes within the cell. Importantly, disruption of the membrane structure, either through increase or decrease of cardiolipin concentration in the membrane, is known to play a central role in a variety of diseases, including cancer. Hence, understanding how membrane structure and dynamics are affected by cardiolipin composition is of immediate importance to multiple areas of research.
Membranes that contain cardiolipin have unique properties; however, there are lingering doubts about whether cardiolipin directly contributes to structural differences between inner and outer mitochondrial membranes. In addition, there are questions about how natural fluctuations in cardiolipin concentration alter the structure and dynamics of those membranes. In our study, we use atomistic molecular dynamics simulations to explore how changing the concentration of cardiolipin alters the structure and lipid dynamics of model mitochondrial membranes. We envisage the simulations as a computational microscope, allowing us to observe and quantitate the behavior of cardiolipin within membranes.
Our cover image for the August 6 issue of Biophysical Journal features a cartoon-like representation of the mitochondrion (left) along with renderings of some atomistic models used in our study (center-right). Among the atomistic model renderings, the centrally placed cardiolipin molecule emphasizes its role in our study and displays the lipid’s unique structure, while the overhead views of the bilayer patches with cardiolipin featured in orange (other lipids in green) embody the key focus in our study on exploring how changing the concentration of cardiolipin altered membrane properties.
- Blake Wilson, Arvind Ramanathan, Carlos Lopez