Increasing affinity between interferon gamma and its receptor by computer design of receptor mutations. I. Design of the mutations

Bohdan Schneider, Jiří Černý, Lada Biedermannová, Pavel Mikulecký, Jiří Vondrášek, and Peter Šebo

Institute of Biotechnology AS CR, v. v. i., Vídeňská 1083, CZ-142 20 Prague, Czech Republic

bohdan@img.cas.cz, http://www.structbio.eu/BS

Rational design of molecules with function changed in desired direction is still a challenge. We intend to design interferon gamma receptor molecules that bind more strongly to their natural ligand, interferon gamma (IFNg), using simple computer models. The IFNg/receptor system is used as a model because it is important for innate and acquired immunity in vertebrates and its targeted modification can lead to practical applications. The model is also suitable because crystal structures of the IFNg/receptor complex are available.

We performed mutation analysis at the models of IFNg/receptor interface determined from crystal structures using empirical force filed as implemented in web-based tool FoldX (http://foldx.crg.es/). The analysis lead to predictions of receptor mutants that should strengthen the interaction. Only residues with lower than 50% conservation were allowed to mutate; the final set of suggested mutations contained nine single mutants, four double and one triple mutant. To check non-random nature of alleged improvement of the binding affinity we also selected four single mutants that should lower the affinity. All eighteen receptor mutants were successfully expressed and their affinities determined, results are shown in a presentation by Mikulecký et al.

Acknowledgements. Support from grant P305/10/2184 from the Czech Science Foundation is greatly acknowledged. All authors are supported by institutional grant AV0Z50520701.