An unrooted phylogenetic tree depicting the evolutionary relationships among the members of the UCP family. Colors illustrate the six major classes into which the proteins cluster. The key to nomenclature can be found in Table 1. Evolutionary distances were calculated from the sequence alignment applying the Jukes-Cantor correction method and the tree was constructed using the Neighbor-Joining method. The dotted lines indicate the more distant relationship of the UCP4 and BMCP1 proteins to the other UCPs.