Figure 4.

Effect of the αI α1-helix mutations on α_Lβ₂ conformational change. HEK293FT cells were transfected with the indicated combination of α_L and β₂ constructs. The cells were incubated with mAb m24 (A) that reports α_Lβ₂ headpiece opening or KIM127 (B) that reports α_Lβ₂ extension in the presence of 1 mm Ca²⁺/Mg²⁺ (Ca/Mg) or 0.2 mm Ca²⁺ plus 2 mm Mn²⁺ (Ca/Mn). The mAb binding was measured by flow cytometry and presented as the MFI normalized to α_Lβ₂ expression measured by TS2/4 binding. The data are means ± S.D. (n ≥ 3; except for αl-K149A and αl-F153W, n = 2). Two-tailed t tests were used to compare the wild type and the mutants in the same conditions or as indicated. *, p < 0.05; **, p < 0.01; ***, p < 0.001. The numbers of percentages indicate the decreased levels of mAb binding.