Cyclin E1 and cyclin E2 are similar proteins, but are independently conserved in vertebrate organisms. A. Homo sapiens cyclin E1 and cyclin E2 proteins were aligned and percentage similarity calculated using ALIGN . The sequences have 48.6% identity overall, with higher identity within the well-conserved cyclin box (75.0%), and less conservation in the N-terminal (45.6%) and C-terminal regions (29.6%). NLS = nuclear localisation sequence, CLS = centrosome localisation sequence, P = phosphorylation site. B. Cyclin E from invertebrates was compared to cyclin E1 and cyclin E2 from several vertebrate organisms. The sequences were aligned using CLUSTALW and the GONNET matrix , and a phenogram derived of the alignment using the DRAWTREE application of the PHYLIP package . The phenogram was visualised with the application TREEVIEW . The scale bar indicates 0.1 amino acid changes per character.