Structural characterization of glycinamide-RNase-transformylase T from .

Enzymes from the purine salvage pathway in () have been regarded as an attractive target for the development of anti-bacterial drugs. Although this pathway has not been extensively studied in , it has been identified as essential for growth and survival. Glycinamide-RNase-transformylase T (PurT) is found only in some specific bacteria including and utilizes ATP-dependent ligation to catalyze the formylation of 5'-phosphoribosyl-glycinamide (GAR) in the third reaction of the de novo purine salvage pathway. In the study, we determined the crystal structure of PurT at a resolution of 2.79 Å. In contrast to PurT (phBCCPPurT), PurT exhibits an "open" conformation, which results in a broader ATP-binding pocket and thus might facilitate the entry and exit of the cofactor. Additionally, active site superposition with PurT (PurT) showed that residues involved in the ATP-binding site in PurT exhibited structural similarity but had notable difference in the GAR-binding site. The loop 383-389 in PurT was much shorter and shifted 5.7 Å away from the phosphate of the GAR substrate. The different GAR-binding mode might result in a large conformational change in PurT, and would provide a possible opportunity for anti-TB drug development.