The Rb C-terminal domain is required for high-affinity binding to E2F-DP complexes and for maximal repression of E2F-responsive promoters, thereby acting as a growth suppressor by blocking the G1-S transition of the cell cycle. This domain has a strand-loop-helix structure, which directly interacts with both E2F1 and DP1, followed by a tail segment that lacks regular secondary structure [1].

1: Structure of the Rb C-terminal domain bound to E2F1-DP1: a mechanism for phosphorylation-induced E2F release. Rubin SM, Gall AL, Zheng N, Pavletich NP; Cell. 2005;123:1093-1106. PMID:16360038