The structure of Zn-bound SsTroA was determined using the molecular replacement method as implemented in Molrep [61] using TpTroA as the search model (PDB entry 1K0F). The structure was rebuilt and refined using COOT [62] and REFMAC5 program [63] . The crystals belong to the P4 3 space group (a = b = 102.4Å , c = 107.3 Å , a = b = c = 90u). The final refined structure without water molecules was used as an initial model for the complex structure. REFMAC5 [63] was again used in conjunction with COOT [62] to refine and build the complex crystal structure. The data collection and final refinement statistics are given in Table S3 . Final models were validated using PROCHECK [64] , and structure figures were generated by PyMOL, unless otherwise noted. Zn-SsTroA was deposited in the Protein Data Bank (PDBID: 3MFQ).