Coevolution of Mucosal Immunoglobulins and the Polymeric Immunoglobulin Receptor: Evidence That the Commensal Microbiota Provided the Driving Force
Figure 6
Interspecies similarity in mucosal Ig and pIgR protein sequences from 10 representative vertebrate species. Alignments in amino acid sequences correspond to the phylogenetic trees shown in Figure 5. (a) Numbering of mucosal Ig amino acids corresponds to the sequence of human IgA1, beginning with the first residue of the variable domain. CH: heavy chain constant region domain. (b) Numbering of pIgR amino acids corresponds to the sequence of human pIgR, beginning with the first residue of the leader peptide. TM: transmembrane. For both alignments, the intensity of shading at each position signifies the degree of similarity among mucosal Ig or pIgR sequences from different species. Gaps in sequence alignments signify regions of limited interspecies homology. Approximate boundaries are noted of key structural elements in mucosal Ig and pIgR proteins.
