The phosphoenolpyruvate-dependent sugar phosphotransferase system (sugar PTS), a major carbohydrate active transport system, catalyzes the phosphorylation of incoming sugar substrates concomitantly with their translocation across the cell membrane. The enzyme II FruAB PTS system is involved in fructose transport. D-fructose(out) + N(pros)-phospho-L-histidyl-[protein] = D-fructose 1-phosphate(in) + L-histidyl-[protein] By fructose. The PTS EIIB type-2 domain is phosphorylated by phospho-EIIA on a cysteinyl residue. Then, it transfers the phosphoryl group to the sugar substrate concomitantly with the sugar uptake processed by the PTS EIIC type-2 domain. In the N-terminal, the PTS system fructose-specific possesses a duplicated EIIB domain (EIIB' domain) which lacks the active site and functions to facilitate phosphoryl transfer between the EIIA domain of diphosphoryl transfer protein (DTP) and the EIIB domain. The presence of the EIIB' domain is required for normal high affinity recognition of DTP by the PTS system fructose-specific as well as for normal rates of phosphoryl transfer between the EIIA and EIIB domains of DTP and PTS system fructose-specific, respectively. The EIIC type-2 domain forms the PTS system translocation channel and contains the specific substrate-binding site.