Structure-based sequence alignment of Amph-2, Onc, RC-RNase, RC-RNase-61 and RNase A. Elements of secondary structure are shaded (α-helices, magenta; (β-strands, cyan) and labeled below. In the RC-RNase and RNase A sequences, residues shown crystallographically to form the B1 and B2 subsites are white and orange, respectively, while those that form the P1 subsite are encircled. Amph-2 residue numbers are given above the sequences and RNase A residue numbers below. The length of each protein sequence is given at its end. <Q, pyroglutamate. Recent crystallography study on Onc in complex with nucleic acid [33]confirmed Lys9, His10, Lys31 and His97 at the enzyme P1 subsite, Lys33, Thr35, Asp67 and Phe98 at the B1 as well as Thr89 and Glu91 in the B2 subsite. Reprinted with permission from [2], modified.