Garcia, Maria TeresaCarreño, DavidTirado-Velez, JMFerrandiz-Avellano, Maria-JoseRodrigues, LilianaGracia, BegoñaAmblar, MonicaAinsa, José Ade la Campa, Adela G2020-02-212020-02-212018Front Microbiol. 2018 Jul 24;9:1659.1664-302Xhttp://hdl.handle.net/20.500.12105/9121The spread of multidrug-resistant isolates of Mycobacterium tuberculosis requires the discovery of new drugs directed to new targets. In this study, we investigated the activity of two boldine-derived alkaloids, seconeolitsine (SCN) and N-methyl-seconeolitsine (N-SCN), against M. tuberculosis. These compounds have been shown to target DNA topoisomerase I enzyme and inhibit growth of Streptococcus pneumoniae. Both SCN and N-SCN inhibited M. tuberculosis growth at 1.95-15.6 μM, depending on the strain. In M. smegmatis this inhibitory effect correlated with the amount of topoisomerase I in the cell, hence demonstrating that this enzyme is the target for these alkaloids in mycobacteria. The gene coding for topoisomerase I of strain H37Rv (MtbTopoI) was cloned into pQE1 plasmid of Escherichia coli. MtbTopoI was overexpressed with an N-terminal 6-His-tag and purified by affinity chromatography. In vitro inhibition of MtbTopoI activity by SCN and N-SCN was tested using a plasmid relaxation assay. Both SCN and N-SCN inhibited 50% of the enzymatic activity at 5.6 and 8.4 μM, respectively. Cleavage of single-stranded DNA was also inhibited with SCN. The effects on DNA supercoiling were also evaluated in vivo in plasmid-containing cultures of M. tuberculosis. Plasmid supercoiling densities were -0.060 in cells untreated or treated with boldine, and -0.072 in 1 × MIC N-SCN treated cells, respectively, indicating that the plasmid became hypernegatively supercoiled in the presence of N-SCN. Altogether, these results demonstrate that the M. tuberculosis topoisomerase I enzyme is an attractive drug target, and that SCN and N-SCN are promising lead compounds for drug development.engVoRhttp://creativecommons.org/licenses/by/4.0/DNA supercoilingDNA topoisomerase I inhibitorMycobacterium tuberculosisN-methyl-seconeolitsineAntituberculosis activityDrug discoverySeconeolitsineAtribución 4.0 Internacional300876659165910.3389/fmicb.2018.01659Frontiers in microbiologyopen access