Fig. 3. Two different integrin headpiece conformations. A representative projection average from (A) unliganded and (D) liganded α₅β₁ headpiece was used to identify the best-correlating projections calculated from a 25 Å density map created from α_Vβ₃ headpiece models (B and E). The model for the open α_Vβ₃ headpiece was prepared as described in the text and Materials and methods section. The models are shown in CPK representation (C and F) using the same color code as in Figure 1A.