Fig. 1. Protein sequence alignment between Mytilus edulis (upper) and M. galloprovincialis (lower) precollagen D. Major domain structures are boxed and indicated. Single amino acid substitutions are indicated by bold italic type, and dashed lines indicate sequence deletions. Histidine residues that may form metal chelate cross-links are in bold type. Breaks or kinks in the collagen repeat structure are symbolized with a filled circle.