A flexible kink in β3 TMD reduces transmission of talin-induced TMD topology change and integrin activation. (A) Emission spectra of β3(L694C)-bimane nanodisc (left) in the presence of increasing concentrations of THD compared with those of β3(A711P,L694C)-bimane nanodisc (middle). Similar fluorescence intensities the in presence of 2% SDS are shown on the right. Fluorescence normalized to the maximum fluorescence intensity of L694C-bimane in the absence of talin is shown. (B) Emission spectra of β3(I721C) and β3(A711P,I721C)-bimane nanodiscs were analyzed as in A. (A and B) Data are representative of at least three independent experiments. (C) Effects of β3(A711P) mutation in response to THD. β3(A711P) breaks the TMD helix into two helices connected by a flexible kink; the flexible kink inhibits the transmission of THD-induced increased embedding across the membrane. (D) CHO cells stably expressing αIIbβ3 or αIIbβ3(A711P) were transfected with THD or vector (vec), and αIIbβ3 activation was measured after 24 h. The arrowhead indicates the band corresponding to THD (∼50 kD). Error bars are SEM of three independent experiments.