Figure 4.

CDK4 interacts with a N-terminal region of A3B. A, amino acid alignment of A3B_NTD and A3A with chimeric junctions indicated in red and structural elements shown above the alignment (α helices, β strands, and loop regions). B, ribbon schematic overlay of the crystal structures of A3B_NTD (red, PDB 5TKM) and A3A (gray, PDB 4XXO). A3B_NTD residues 80–85 are highlighted in blue (see text for details). C, anti-Flag (CDK4) co-IP of indicated Strep-tagged A3B_NTD constructs from 293T cells. Parallel reactions were done with empty vector and A3A-S as negative controls. See Fig. 2A legend for a description of the IP labeling scheme.