Fig. 1.

Scoring of symmetry in the yeast mitochondrial phosphate transporter ScPic2p. (A) The alignment of the even-numbered α-helices in ScPic2p. Highlighted in color are 2 examples of symmetry-related triplets of residues, as used in B and C. (B and C) The replacement scores (black) for each comparison in the triplet were obtained from the residue replace ability matrix (55). The symmetry score of a residue (green) is the average of the 2 replacement scores. (B) Triplet E-E-D with symmetric residues. (C) Triplet K-V-K with an asymmetric valine residue. (D) The cumulative frequency distribution of the symmetry scores for all possible triplets in the sequences of the subfamily of fungal Pic2p transporters. The symmetry scores are defined by a red-white-blue color scale, in which the median of the distribution is white and the minimal and maximal symmetry scores red and blue, respectively (Fig. 2 A and B). The symmetry scores of D288 (B) and V191 (C) (conservation scores in brackets) are shown.