Research Interests:

The long term goal of our research is to understand how the environment of biological membrane affects function of proteins residing in it.

Membrane proteins represent about 30% of all proteome and perform essential functions, including energy conversion, signal transduction, and chemical transport in and out of cells. Numerous diseases are associated with reduction or loss of function in membrane proteins, and many pathogens exploit membrane receptors to facilitate entrance inside the cells. About 60% of approved drugs on the market act on membrane proteins.

Rational design of new drugs with better efficacy and selectivity requires knowledge of a detailed 3-dimensional structure of the target protein at atomic resolution, however, the number of solved membrane protein structures is far smaller than that of soluble proteins. Success in crystallization of eukaryotic and, in even larger degree, of human membrane proteins is limited by the challenges in heterologous expression of functional proteins and by the low stability of these proteins when purified in detergent solution. Both of these problems relate to intimately more complex nature of biological membranes of higher organisms.

Multiple lipid components and intrinsic heterogeneity of biological membranes provide tight control of function and selective stabilization of embedded proteins. One of the main players in maintaining heterogeneity in biological membranes is cholesterol, an ubiquitous lipid in eukaryotic cells. Activities of a large number of proteins from different families were found to be directly modulated by cholesterol, yet there is no clear understanding of a structural mechanism of cholesterol action on membrane proteins.

In our research we use lipidic cubic phase (LCP) as a primary tool to study lipid/protein interactions and to crystallize membrane proteins directly from the lipidic environment. Our targets include G protein-coupled receptors (GPCR), ion channels and transporters.

In order to achieve our goals we are developing an LCP-toolchest: collection of assays and methods to interrogate behavior of proteins and their interaction with lipids in LCP. In addition to providing insights into the lipid/protein interactions these assays implement convenient metrics to guide protein engineering, selection of ligands and lipids for improving chances for crystallization and expanding high-resolution structural coverage of elusive human membrane proteins.