FIGURE 1.

Interspecies (bovine-mouse) alignment of the amino acid sequences of SLO3 channel paralogues. Identical residues are shaded. A comparison of Fig. 1 and supplemental Fig. S1 reveals that SLO3 paralogues are highly divergent (62.1% identity) relative to SLO1 paralogues (98.2% identity) in the same species, suggesting a more rapid rate of evolution. Unusually rapid evolutionary change is characteristic of genes involved in sexual reproduction and especially in male reproduction. Hydrophobic segments surrounding the pore region are designated S0–S6. The limits of the bSLO3 sequence incorporated into chimera 3 are indicated by filled blue circles. The mSLO3-A, mSLO3-B, and mSLO3-C chimeric regions are indicated by red bars designated A, B, and C, respectively (see text). SLO3 and SLO1 channels have similar voltage sensors (underline S4) (15). The “calcium bowl” Ca²⁺-sensing site (16) present in SLO1 is not present in SLO3.