Figure 4

Deduced amino acid sequences of Amphiura filiformis opsins (names in bold in the figure) aligned with Strongylocentrotus purpuratus opsins and Rattus norvegicus rhodopsin. Alignment is limited to two highly conserved regions including the “DRY-type” tripeptide, the opsin-specific lysine residue, and the “NPxxY(x)₆F” pattern. Predicted transmembrane alpha-helices are underlined in red. The lysine residue involved in the Schiff base formation – equivalent to K296 of the R. norvegicus rhodopsin - is highlighted in red in the alignment. The tyrosine residue (Y) in the position equivalent to the glutamate counterion E113 in R. norvegicus rhodopsin, and the DRY-type tripeptide motif (E134/R135/Y136 in R. norvegicus rhodopsin) is highlighted in blue. The pattern “NPxxY(x)₆F” (position 302–313 of the R. norvegicus rhodopsin sequence) is highlighted in green. The amino acid triad (in the equivalent position 310–312 in the R. norvegicus rhodopsin) belong to the pattern NPxxY(x)6F. The “NxQ” motif, classically observed in c-opsins is written in red in the alignment and the “HxK” motif, classically observed in r-opsins, in blue. Other amino-acid residues that are highly conserved in the whole opsin family are shown with a grey background. See text and Additional file 3 for more details. Numbers indicated in gray on the left side of each aligned region correspond to the position number of the first amino acid of the considered sequence.