Fig. 1. The primary sequence of HPV16 E7 oncoprotein is drawn with two conserved regions (CR1, CR2), L₂₂XCXE₂₆ motif (sky blue) that binds with the B-box of pRb, CR3 and two conserved Zn-binding motifs (C₅₈XXC₆₁, C₉₁XXC₉₄, Cys marked in yellow) within CR3. The boxes in CR3 indicate the secondary structures.