Crystal structure of the polyketide cyclase from Mycobacterium tuberculosis

About 40% of proteins are classified as conserved hypothetical proteins in Mycobacterium tuberculosis (TB). Identification and characterization of these proteins are beneficial to understand the pathogenesis of TB and exploiting novel drugs for TB treatments. The polyketide cyclase, a protein from M. tuberculosis (MtPC) has been annotated as a hypothetical protein in Uniprot database. Sequence analysis shows that the MtPC belongs to the NTF2-like superfamily proteins with diverse functions. Here, we determined the crystal structure of MtPC at a resolution of 2.4 angstrom and measured backbone relaxation parameters for the MtPC protein. MtPC exists as a dimer in solution, and each subunit contains a six-stranded mixed beta-sheet and three a helixes which are arranged in the order alpha 1-alpha 2-beta 1-beta 2-alpha 3-beta 3-beta 4-beta 5-beta 6. The NMR dynamics analysis showed that the overall structure of MtPC is highly rigid on ps-ns time scales. Furthermore, we predicted the potential function of MtPC based on the crystal structure. Our results lay the basis for further exploiting and mechanistically understanding the biological functions of MtPC.