Figure 1.

Both the C₂A and C₂B domains of synaptotagmin I have a conserved basic residue at the tip of the Ca²⁺-binding pocket. A, Alignment of synaptotagmin I from human, rat, mouse, and Drosophila. Bars indicate β-sheets, ⊕ indicates the conserved basic residues, dots indicate Ca²⁺-binding residues, and open boxes indicate conserved hydrophobic residues. Within the alignment, conserved residues are shown in gray, and identical residues are boxed. B, Schematic representation of loops 1 and 3, which form the Ca²⁺-binding pockets of both C₂ domains [adapted with permission from Fernandez et al. (2001), their Fig. 6, using the Drosophila sequence to show the conserved basic residues (⊕) examined in this study].