Innovative extraction to crystallization technology of functional membrane proteins in solution – MPEC

The global protein therapeutics market will be worth $77 billion (bn) by 2011 (RNCOS, 2010, May). Beside, the global proteomic market is expected to increase from $7.9 bn in 2009 to $19.4 bn in 2014, for a compound annual growth rate of 19.7 % (BCC Research Report, 2009, June). This market deeply depends on membrane proteins as about 2/3 of the pharmaceutical targets belong to that type of proteins (Overington 2005), a ratio which is estimated to increase to 3/4. However the current strategies of membrane protein structure-based drug design remain limited by the paucity of crystal structures of membrane proteins. Indeed they account for 30 % of proteins but only 1 % of solved structures, this last ratio remaining constant. In addition, the efficacy of antibodies raised against membrane proteins directly depends of their folding (Frokjaer & Otzen 2005). This is due to the fact that, on the one hand, membrane proteins are unstable outside their lipid environment and in the other hand that the available detergents for extracting membrane proteins do not stabilize them enough along the process of extraction, purification to crystallization.

To bring a solution to that problem, we have developed during the last three years in the frame of the ANR-06-PCVI-0019-01 “Stabicalix” project, an innovative technology using a new concept of supramolecular surfactants structuring the membrane domain. Contrarily to classical detergents, they can generate a network of salt bridges involving the bulk of positively charged residues located at the cytosol-membrane interface of membrane proteins, rather abundant in that region. Such detergents increase the membrane domain cohesion during extraction, purification and crystallization processes as we successfully showed it with a multidrug resistance (MDR) ATP-binding Cassette (ABC) transporter, which, for the first time could be active after extraction. This research has been validated by two patents (Coleman, Falson 2008 ; Matar, 2009), a first publication (Suwinska 2008) and a second main one currently in the revision process (Matar, - ).

In that context, the aim of the MPEC project is to validate the use of this innovative technology with a panel of 16 different membrane proteins, main of them representing critical pharmaceutical targets: ABC multidrug efflux pumps involved in anti-cancer and anti-infectious drug resistances and Resistance–Nodulation–cell Division (RND) bacterial multidrug efflux pumps involved nosocomial infections, GPCRs which represent 1/4 of the total pharmaceutically-addressed drug targets, mitochondrial carriers and channels. Two teams, both recognized at national and international levels in the field, manipulating and crystallizing different membranes proteins are associated to the former one to carry out such a validation. Together, teams will test the technology with approaches covering extraction, stabilization, purification biophysical characterization and crystallization of these proteins routinely handled in each lab.

Our technology offers important possibilities in term of protein study to therapeutic aim and this fact present a strong societal impact. A spin-off “Calixar” will be created to carry out the economic development of the technology.