Crystal structure of the polyketide cyclase from <italic>Mycobacterium tuberculosis</italic>

<?A3B2 tlsb=.01w?>About 40% of proteins are classified as conserved hypothetical proteins in <italic>Mycobacterium tuberculosis</italic> (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 <italic>M. tuberculosis</italic> (<italic>Mt</italic>PC) has been annotated as a hypothetical protein in Uniprot database. Sequence analysis shows that the <italic>Mt</italic>PC belongs to the NTF2-like superfamily proteins with diverse functions. Here, we determined the crystal structure of <italic>Mt</italic>PC at a resolution of <sc>2.4 Å</sc> and measured backbone relaxation parameters for the <italic>Mt</italic>PC protein. <italic>Mt</italic>PC exists as a dimer in solution, and each subunit contains a six-stranded mixed β-sheet and three α helixes which are arranged in the order α1-α2-β1-β2-α3-β3-β4-β5-β6. The NMR dynamics analysis showed that the overall structure of <italic>Mt</italic>PC is highly rigid on ps-ns time scales. Furthermore, we predicted the potential function of <italic>Mt</italic>PC based on the crystal structure. Our results lay the basis for further exploiting and mechanistically understanding the biological functions of <italic>Mt</italic>PC.<?A3B2 tlsb?>