D22 - Protein-lipid Interaction

COST Action D22 was conceived with the aim of increasing the knowledge of protein-lipid interactions on molecular level and time scales, based on an interdisciplinary approach by chemists, physicists and biologists. This COST Action has allowed the collaboration between 36 research groups from 18 different countries.

Protein-lipid interactions are essential features of biological membranes, nevertheless many questions related to the chemistry and physics of lipids and proteins are still not understood nowadays. The lack of proper understanding of molecular mechanisms important for the functioning of biological membranes also hinders practical industrial applications. The scientific goals of Action D22 can be summarised as follows: integration of chemical and physical knowledge of biological membranes and protein-lipid systems; better understanding of molecular processes and time scales important for the functioning of biological membranes, with emphasis on structural aspects of lipids and proteins, protein association and membrane domain formation using different membrane model systems; and reinforcement of research efforts by links between academic institutions and industries.

Molecular simulation has developed substantially over the time-frame of Action D22. Initially considered a rather inexact and unreliable approach, the sophistication of the methodology has improved significantly to the point that such studies suggest interesting structure/function relationships and mechanisms of action which are a great stimulus to experimentation. The Action has attracted physicists as well as theoretical chemists and computational biologists, making for interesting diversified views on essentially the same system. D22 has also incorporated bioinformatics and it has been from this that the most significant “tour-de-force” has come with the identification of the cellular locations of the C-terminal regions of almost all membrane proteins encoded by the genomes of Escherichia coli and Saccharomyces cerevisiae. Considerable progress was also made through simulations of the mechanisms of insertion of peptides and proteins into the lipid bilayer, and their interactions with and effects on lipid behaviour.

Action D22 has undertaken as well the characterisation of raft-like domains in model membranes by fluorescence microscopy and spectroscopy allowing the construction of phase diagrams and the characterisation of the dynamics of raft-like domains. Using EPR, the first direct demonstration of liquid-ordered/liquid-disordered phase coexistence in a binary mixture was demonstrated. NMR, calorimetry and EPR studies gave new insights into the interactions between raft components, such as the effect of cholesterol on the lateral diffusion of lipids and the specificity of the interactions between sphingolipids and cholesterol.

Methodology has also been developed for the use of time released FRET for lipid domain size, for the preparation of giant unilamellar vesicles from native membranes and for reconstituting integral membrane proteins into these vesicles. By employing single molecule microscopy, movement, cluster formation and co-localization of molecules was investigated and a novel single molecule technology was established for measuring the composition of individual lipid rafts in intact cells.