FIGURE 4.

phosRbPL binds the pocket domain at the E2F^TD binding site. A, structure of E2F^TD bound to the pocket domain. Critical contacts between Asp⁴²⁴ and Phe⁴²⁶ of E2F and Arg⁴⁶⁷ and Phe⁴⁸² of Rb are shown. This figure was generated using Protein Data Bank entry 1N4M. B and C, HSQC spectra of 100 μm ¹⁵N-labeled phosRbPL^592–624 alone (black) and in the presence of 500 μm unlabeled RbP^ΔPL-R467A (red) and RbP^ΔPL-F482A (blue), respectively. D, resonance peak intensity ratios of phosRbPL in the presence of wild type RbP^ΔPL (black) and mutants R467A (red) and F482A (blue). The ratio I/I₀ is defined as the peak intensity of phosRbPL in the presence of RbP^ΔPL (I) divided by the peak intensity of phosRbPL alone (I₀). These data demonstrate that Arg⁴⁶⁷ and Phe⁴⁸² in the pocket domain are critical for binding phosRbPL as well as E2F^TD.