The MdtABC tripartite complex confers resistance against novobiocin and deoxycholate. Part of a tripartite efflux system composed of MdtA, MdtB and MdtC. MdtB forms a heteromultimer with MdtC. The mdtABC operon is transcriptionally activated by BaeR. Belongs to the resistance-nodulation-cell division (RND) (TC 2.A.6) family. MdtB subfamily.