General structural features that regulate integrin affinity revealed by atypical αVβ8

Integrins αVβ8 and αVβ6 are master activators of proTGF-βs. Whereas most integrins including αVβ6 are activated by tensile force applied by the cytoskeleton, αVβ8 links differently to the cytoskeleton and lacks the open headpiece conformation that represents the high affinity state of other integrins. Here, we shed light on the atypical activation mechanism of integrin αVβ8 using crystal structures in the absence and presence of proTGF-β1 peptide, comparisons of the hydrogen deuterium exchange dynamics of αVβ8 and αVβ6, and affinity measurements on mutants in which structurally atypical residues of αVβ8 and typical residues of αVβ6 were reciprocally exchanged.