Figure 1.

Alignment of so/Six homologues homeodomain amino acid sequences of mouse used to represent vertebrates and of Drosophila and Caenorhabditis elegans used to represent invertebrates. The secondary structure of the domains is shown at the top of the figure. Amino acid identities for representative genes of the so/Six family are compared with the Drosophila so homeodomain (10). Sequences used in this comparison include: mouse Six1, Six2, and Six3 (12); Six4 (26); Drosophila optix/Six3 and Six4 (27, 28); and the nematode C. elegans Ceh-32, Ceh-33, and Ceh-34 (EMBL database). The tetrapeptides used to classify the sine oculis homeodomains in three families are indicated in bold and boxed. Percentages of sequence identity (%ID) and similarity (%S) were determined by comparison to Drosophila so and are indicated to the right of the sequences.