Fig. 1. Structures of Shot isoforms. (A) The F-actin/microtubule crosslinking Shot isoforms required for axon extension. The Shot L(A) isoform contains an N-terminal actin-binding domain, a central domain of 4000 amino acids and a C-terminal domain that contains EF-hand Ca²⁺-binding motifs, the GAS2 motif and other conserved sequences. The central domain contains a plakin-like region and 22 spectrin repeats (Strumpf and Volk, 1998). Numbers indicate the start and end positions of the different domains in the amino acid sequence and the percent amino acid identity between Drosophila Shot L(A) and mouse ACF7 (Leung et al., 1999) in the N-terminal, central and C-terminal domains. The other Shot isoform that crosslinks F-actin and microtubules, Shot L(B), differs from Shot L(A) only in the N-terminal leader sequence. ABD, actin-binding domain; EF, EF-hand; GAS2, GAS2 homology motif. (B) The structures of the four Shot N-terminal domains (Lee et al., 2000). Numbers indicate the start and end positions of the different features in the amino acid sequence. Type A and type B N-terminal domains differ in their leader sequences (residues 1-143 and 1-32, respectively) and contain two calponin homology motifs (CH1 and CH2). The type C domain contains yet another leader sequence (residues 1-210) and only the CH2 motif. The type D domain starts in the central rod domain.

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