Figure 6

Comparison of wild-type active sites with transfer models HisF(template) → HisA(scaffold) and TrpF(template) → HisF(scaffold) determined by TransCent. The catalytic residues in native HisF (A, 1thf) and the designed residues of the HisF → HisA transfer (B) are shown in complex with PRFAR (HisF substrate and HisA product). The designed residues in the HisA scaffold are located at equivalent positions as in the HisF template (compare panel B and A). The catalytic residues in native TrpF (C, 1lbm) and the corresponding residues of the designed TrpF → HisF model (D) are shown in complex with rCdRP (product analogue of TrpF). In wild-type TrpF, Cys 7 is located on β-sheet 1, and Arg 36 is located on a long loop after β-sheet 2. In the model, an arginine residue, which is responsible for ligand binding, is placed in the elongated β-sheet 1 (D11R exchange), whereas the catalytic cysteine (V48C exchange) is located in β-sheet 2. The aspartic acid D126 (TrpF) and the designed exchange T171D (TrpF → HisF transfer) are located at equivalent positions.