Identification of three 2TMS homologous repeat sequences in the 6TMS CDF antiporters. (A) Alignment of CDF TMSs 1-2 of Aod (Actinomyces odontolyticus, gi# 154507747) with CDF TMSs 3-4 of Ssa (Staphylococcus saprophyticus, gi# 73662044). (B) Alignment of CDF TMSs 3-4 of Ilo (Idiomarina loihiensis, gi# 56460742) with CDF TMSs 5-6 of Bsp (Bacillus sp. B14905, gi# 126652939). The IC program was used to identify internal segments exhibiting the greatest statistical similarity . The GAP program  was used to generate the alignment with default settings and 500 random shuffles). Numbers at the beginning and end of each line indicate residue numbers in the proteins. |, identity; :, close similarity; ., more distant similarity as defined by the GAP program. This convention of presentation is also used in Figures 3 and 4. In all three figures, positions of the TMSs were predicated using the TMHMM program.