RB1 and neoplasm: The wild-type C-helix sequence of CDK2 bindingto cyclin E was selected because: (i) helical mimicry for CDK2·cyclinE is new; (ii) it is illustrative of PPIs which lead to phosphorylationof retinoblastoma protein (Rb, phosphorylation of which to pRb “liftsthe suppression handbrake” and leads to uncontrolled cell cyclingand growth in many tumor types48,49); and (iii) the 13-residueCDK2 C-helix system is not long enough to fold intoa helix in aqueous solution but has sufficient residues to accommodatetwo capping motifs.