Figure 1. Summary of IRBP gene structure and location of the Arg->Gln substitutions

(A) Map of the IRBP gene with exons represented as rectangles and introns as interrupted lines. The first exon codes for protein modules 1 through 3 and part of module 4. The remainder of the fourth module is composed of segments derived from exons 2 through 4. Each module consists of ~300 amino acid residues. (B) Similarity plot of the C-terminal modules of human [22], bovine [27] Xenopus [20] and zebrafish [26] IRBPs. The stippled regions under the plot have a similarity score > 1.0. The positions of the Arg->Gln substitutions presented in this paper are indicated. Portions of this figure have been modified from Baer et al. [48].