Lys¹¹⁵¹ within the integrin α1 tail is required for endothelial cell adhesion, migration, and tubulogenesis, but not proliferation. Cell adhesion (A), migration (B), tubulogenesis (C), and proliferation (D) were determined as described in Figures 1 and 2. (E,F) Integrin α1β1–dependent signaling and densitometry analysis were determined as described in Figure 2C,D. * indicates statistically significant differences (P < .05) between the α1KO and the α1 mutant–expressing endothelial cells.