Alignment of the 4 full-length I ricinus serpin clones with their orthologs from I scapularis obtained from the completed I scapularis genome. All serpins are compared with IRIS, the only functionally characterized tick serpin so far. Unlike IRIS, IRS-2 has a clear signal peptide (residues 1-21). The secondary structure elements are indicated according to the IRS-2 crystal structure: α-helixes (cylinders), β-strands (arrows); the hatched arrow represents the region that undergoes a conformational change from a loop to a β-strand after proteolytic cleavage of RCL. SP, signal peptide; hinge, hinge region, an important determinant of serpin inhibitory potential; RCL, reactive center loop; P1 (rectangle), predicted residue behind which the target protease cleaves the RCL.