Investigation of the binding interactions of progesterone using muteins of the human progesterone receptor ligand binding domain designed on the basis of a three-dimensional protein model

The aim of this study was to investigate the binding interactions of the human progesterone receptor (hPR) with its natural ligand. Therefore, a homology-derived model of the hPR ligand binding domain has been constructed and used to predict residues potentially involved in interactions with progesterone. These residues and the free cysteines have been mutated (in total 13 residues with 15 mutations). All exchanges have been designed to preserve the three-dimensional structure of the protein. With respect to the binding characteristics towards progesterone, the muteins fall into three groups displaying no, reduced, or wildtype-like binding activity.