Energy-coupling factor (ECF) transporters consist of a substrate-specific component (known as the S component), and an energy-coupling module [2]. The substrate-binding component is a small integral membrane protein which captures specific substrates and forms an active transporter in the presence of the energy-coupling AT module.

1: Evolution of the deaminase fold and multiple origins of eukaryotic editing and mutagenic nucleic acid deaminases from bacterial toxin systems. Iyer LM, Zhang D, Rogozin IB, Aravind L; Nucleic Acids Res. 2011; [Epub ahead of print] PMID:21890906

2: A novel class of modular transporters for vitamins in prokaryotes. Rodionov DA, Hebbeln P, Eudes A, ter Beek J, Rodionova IA, Erkens GB, Slotboom DJ, Gelfand MS, Osterman AL, Hanson AD, Eitinger T; J Bacteriol. 2009;191:42-51. PMID:18931129