@article{mbs:/content/journal/micro/10.1099/mic.0.2006/004234-0, author = "Ganas, Petra and Mihasan, Marius and Igloi, Gabor L and Brandsch, Roderich", title = "A two-component small multidrug resistance pump functions as a metabolic valve during nicotine catabolism by Arthrobacter nicotinovorans", journal= "Microbiology", year = "2007", volume = "153", number = "5", pages = "1546-1555", doi = "https://doi.org/10.1099/mic.0.2006/004234-0", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.2006/004234-0", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", keywords = "Kn, kanamycin", keywords = "6-HLN, 6-hydroxy-l-nicotine", keywords = "AO, amine oxidase", keywords = "MABO, γ-N-methylaminobutyrate oxidase", keywords = "2,6-DHP, 2,6-dihydroxypyridine", keywords = "PONH, pseudooxynicotine hydrolase", keywords = "CCCP, carbonyl cyanide m-chlorophenylhydrazone", keywords = "2,6-DHPON, 2,6-dihydroxypseudooxynicotine", keywords = "TPP+, tetraphenylphosphonium", keywords = "SMR, small multidrug resistance", keywords = "LB, lysogeny broth", keywords = "PMF, proton-motive force", abstract = "The genes nepAB of a small multidrug resistance (SMR) pump were identified as part of the pAO1-encoded nicotine regulon responsible for nicotine catabolism in Arthrobacter nicotinovorans. When [14C]nicotine was added to the growth medium the bacteria exported the 14C-labelled end product of nicotine catabolism, methylamine. In the presence of the proton-motive force inhibitors 2,4-dinitrophenol (DNP), carbonyl cyanide m-chlorophenylhydrazone (CCCP) or the proton ionophore nigericin, export of methylamine was inhibited and radioactivity accumulated inside the bacteria. Efflux of [14C]nicotine-derived radioactivity from bacteria was also inhibited in a pmfR : cmx strain with downregulated nepAB expression. Because of low amine oxidase levels in the pmfR : cmx strain, γ-N-methylaminobutyrate, the methylamine precursor, accumulated. Complementation of this strain with the nepAB genes, carried on a plasmid, restored the efflux of nicotine breakdown products. Both NepA and NepB were required for full export activity, indicating that they form a two-component efflux pump. NepAB may function as a metabolic valve by exporting methylamine, the end product of nicotine catabolism, and, in conditions under which it accumulates, the intermediate γ-N-methylaminobutyrate.", }