doi:10.3389/fmicb.2018.01659engGarcía, M.T.Carreño, D.Tirado-Vélez, J.M.Ferrándiz, M.J.Rodrigues, L.Gracia, B.Amblar, M.Ainsa, J.A.de la Campa, A.G.Boldine-derived Alkaloids inhibit the activity of DNA topoisomerase I and growth of Mycobacterium tuberculosisART-2018-107619The 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.2018http://zaguan.unizar.es/record/7497210.3389/fmicb.2018.01659http://zaguan.unizar.es/record/74972oai:zaguan.unizar.es:74972info:eu-repo/grantAgreement/EC/FP7/260872/EU/More Medicines for Tuberculosis/MM4TBinfo:eu-repo/grantAgreement/ES/MINECO/BIO2009-09405info:eu-repo/grantAgreement/ES/MINECO/BIO2017-82951-RFrontiers in Microbiology 9, JUL (2018), 1659 [9 pp]byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess