 The IIB and IIC domains of the fructose porters appear to be dissimilar from each other as those of the mannitol porters.The IIB and IIC domains of these porters are homologous to those of the Glc family.However, the structure of the IIA domain of the mannitol porter of "Escherichia coli" has been determined, and it proved to possess an α2β2α3 secondary structure, a structure which is very different from the β-sandwich structure of IIAGlc.