Component of an efflux pump responsible for the transport of nicotine breakdown products, in particular methylamine, out of the cell. This pump apparently serves as a metabolic valve for nicotine catabolites and may protect the bacteria from the potentially toxic side effects of these compounds. The efflux pump is composed of NepA and NepB. Is transcribed only in the presence of nicotine under the control of the transcriptional activator PmfR. Forms part of an operon with nepB, folD, mabO and purU. Belongs to the drug/metabolite transporter (DMT) superfamily. Small multidrug resistance (SMR) (TC 2.A.7.1) family. NepA/NepB subfamily.