Fig. 1. The phosducin family consists of three defined subgroups. The protein sequences of 33 phosducin homologues were obtained from different organisms. These sequences were aligned (see Supplementary data for protein sequences, DDBJ/EMBL/GenBank entries and complete alignment). (A) Phylogenetic tree. The alignment was used as input for the Phylip program to construct the tree. The numbers indicate bootstrap values. (B) Alignment of three or four members of each subgroup. Residues shaded in black are conserved in 80–100% of all sequences; residues shaded in grey are conserved in 60–70% of all sequences; bold characters are conserved in 75–100% of the sequences of a subgroup only. Substitutions within the following groups were considered as conservative: DE, RK, NQ, ST, FWY and MAILV. The structural elements of HsPhd are indicated as follows: ∼∼∼, flexible loop; ===, α-helix; →, β-strand. The Gβ-contacting residues of HsPhd are denoted by + above the aligned sequences. The start of the thioredoxin-like C-terminal domain is marked by a filled triangle.