Fig. 2
Overview of structures. The structures of all five full-length TtSlyD (TtSlyDFL) and three TtSlyD constructs with the insert-in-flap (IF) domain replaced by the flap loop from human FKBP12 (TtSlyDΔIF) are shown in ribbon representation with the FK506-binding protein (FKBP) domain in white, IF domain in blue, inter-domain loops in orange (TtSlyDFL), and flap loop in black (TtSlyDΔIF). Spheres designate bound anions (chloride is turquoise and sulfate is yellow/red), and pink sticks represent the bound peptides and FK506. All structures are shown in the same orientation and are labeled according to which substrate is bound. Note that the TtSlyDFL:S2 and TtSlyDFL:S2W23A structures display different peptide binding modes for the different TtSlyDFL copies in their asymmetric units. TtSlyDFL:S2 thus presents two different binding modes at the IF domains of TtSlyDFL molecules A and B (both are shown), while TtSlyDFL:S2W23A displays two different binding modes at the FKBP domain of molecules A and C contra molecules B and D (shown for molecules C and D). Additional file 2 shows the binding site for the chloride ion in detail, and Additional file 3 shows a metal binding site that was omitted from the main figure for clarity