Fig. 7. The amino acid sequence of SPE-38 and a visual comparison of the predicted structure of SPE-38 with that of several tetraspan integral membrane proteins that are thought to function in cell-cell interactions. (A) The predicted and aligned amino acid sequences (single letter code) of C. elegans (Ce-SPE-38) and C. briggsae (Cb-SPE-38) SPE-38 proteins. Yellow shading indicates identical amino acids; green shading indicates similar amino acids; predicted transmembrane domains are shown in bold blue letters. The sequence used to generate the anti-SPE-38 sera is underlined, and the first amino acid missing in the spe-38(eb44) mutation (aspartic acid) is indicated by red shading. (B) A schematic representation of Ce-SPE-38 and Cb-SPE-38, and comparisons with other tetraspan integral membrane proteins. Transmembrane domains are indicated with blue boxes; the black arrow indicates the loop domain used for peptide synthesis and the red arrow indicates the aspartic acid residue position in eb44 noted in A. The mutant gene is not predicted to code for any wild-type protein sequence beyond this residue. The schematics for the various proteins are derived from previous reports (Boucheix and Rubinstein, 2001; Heiman and Walter, 2000; Hemler, 2003; Tsukita and Furuse, 1999), and/or from our hydropathy plot and domain structure analysis (see Materials and methods).