DNA helicase B () unwinds duplex DNA with 5'-3' polarity. It has single-strand DNA-dependent ATPase and DNA helicase activities and prefers ATP and dATP as substrates. It may facilitate cellular recovery from replication stress during S phase [, , ].
This family consists of the H+/heavy metal cation antiporters. CzcA has a low cation transport activity for cobalt and is essential for the expression of cobalt, zinc and cadmium resistance. CusA is a part of a cation efflux system that mediates resistance to copper and silver [, ]. NccA is a component of the NCC cation-efflux system that confers resistance to nickel, cobalt and cadmium. It may form a membrane tunnel, which allows ion transport across the membrane. SilA is a component of the sil cation-efflux system that confers resistance to silver. It may be part of a three-component cation/proton antiporter.HelA is presumed to function with HelC and HelB in efflux of an unidentified substrate.The products of the genes cnrA, cnrB, and cnrC are likely to form a membrane-bound protein complex catalyzing an energy-dependent efflux of Ni2+ and Co2+. The mechanism of action of the CnrCBA complex may be that of a proton/cation antiporter.