PROTEO, Université Laval, Québec G1V 0A6, Canada, International AIDS Society HQ, CH-1202 Geneva, Switzerland, Department of Biology, University of Copenhagen, DK-2200 Denmark, Institut de Biologie Structurale, Grenoble F-38027, France, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK, Institute of Organic Chemistry & CMBI, University of Innsbruck, A-6020, Austria and NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, GermanyPROTEO, Université Laval, Québec G1V 0A6, Canada, International AIDS Society HQ, CH-1202 Geneva, Switzerland, Department of Biology, University of Copenhagen, DK-2200 Denmark, Institut de Biologie Structurale, Grenoble F-38027, France, Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK, Institute of Organic Chemistry & CMBI, University of Innsbruck, A-6020, Austria and NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany.