Figure 2

A. C. intestinalis alternative splice variants Talin-a and Talin-b. Exons 47, 48 and 49 encode the C-terminal I/LWEQ module of talin, which is composed of four conserved blocks (black boxes, 1–4 [2]). The alternative exon 49 specifies the 78 C-terminal amino acids of either Talin-a (e49a) or Talin-b (e49b). B. Sequence comparison of Talin-a and Talin-b. The alternative splice site is near the C-terminal boundary of Block 3. The asterisks identify three sequence polymorphisms (E D, S V, and I L) that were found in cDNAs isolated from two separate first-strand cDNA syntheses using total RNA from organisms from the Atlantic population of C. intestinalis, which is isolated from the Pacific population that was used to determine the genome sequence. Red, identical amino acids; blue, conserved changes. C. Multiple sequence alignment of representative chordate talin C-termini. The unique Talin-a and Talin-b sequences, through the final residue of Block 4, were aligned with 10 other chordate talins using CLUSTAL W [19]. Complete description of these sequences is available in reference [3]. Red, identical amino acids; blue, conserved; yellow, similar. D. Chordate I/LWEQ module phylogenetic tree. The guide tree from the alignment of the C-termini of chordate I/LWEQ modules in (C) was used to calculate this unrooted tree [20], which shows both the conservation and divergence of the C-termini of the chordate talins. Vertebrate Talin1 and Talin2 are clustered in two orthologous branches. C. intestinalis Talin-a and the Talin-a ortholog from the tunicate Molgula tectiformis also group together. The sequence divergence of C. intestinalis Talin-b from the other talins is illustrated by the long single branch. Species: Ci, C. intestinalis; Mt, Molgula tectiformis; Hs, Homo sapiens; Xl, Xenopus laevis; Gg, Gallus gallus (chicken); Dr, Danio rerio (zebrafish). Scale bar: 10% sequence divergence.