Crystal structure of Methionyl-tRNA synthetase from Rickettsia typhi in complex with its cognate amino acid.

Rickettsia typhi is the causative agent of murine typhus (endemic typhus), a febrile illness that can be self-contained, though in some cases it can progress to death. The three dimensional structure of Methionyl-tRNA Synthetase from R. typhi (RtMetRS) in complex with its substrate l-methionine was solved by molecular replacement and refined at 2.30 Å resolution in space group P1 from one X-ray diffraction dataset. Processing and refinement trials were decisive to establish the lower symmetry space group and indicated the presence of twining with four domains. RtMetRS belongs to the MetRS1 family and was crystallized with the CP domain in an open conformation, what is distinctive from other MetRS1 enzymes whose structures were solved with a bound methionine (therefore, in a closed conformation). This conformation resembles the ones observed in the MetRS2 family.