Alignment of loop D residues of XIPs. Multiple sequence alignment of residues forming loop D is shown for all XIPs. Residues forming the last turn of H4 and the first turn of H5 are shown in gray background. All basic (Arg, Lys and His) and acidic (Asp and Glu) residues are displayed in red and blue colors respectively. ClustalW (version 1.82) was used to perform the multiple sequence alignment of both loops.