Figure 1
(a) Integrin architecture and potential mechanism for the activation and clustering of integrins. Specific contacts between the ectodomains, the TMH and cytoplasmic domains keep the integrin α (blue) and β (red) subunits proximal in the inactive state. Concomitant with activation, the transmembrane domains become separated and available for homomeric interactions. Homomeric association of the transmembrane domains leads to clustering on the cell surface11. (b) Primary sequence of the integrin β1a-TMC domain depicted with starting and ending residue numbers (V717 and K798). Residues selected for site-directed spin labeling one at a time (P731 to I756) are highlighted by framing in red. (c) SDS-PAGE analysis of integrin β1a-TMC in detergent micelles (left gel) and lipid liposomes (right gel). Lane 1 and lane 3 are molecular size markers. Lane 2 is integrin β1a variant L747C in detergent micelles while lane 4 is the variant L749C in lipid liposomes. L747C in detergent micelles migrated with a molecular weight of approximately 16 kDa as a monomer, while L749C in lipid liposomes migrated as multiple-bands of monomers, dimers and trimers. The gels have been run under the same experimental conditions and were cropped to improve the clarity and conciseness of the presentation. A vertical dividing line was drawn at the splice junction to show non-adjacent lanes in the SDS-PAGE for samples in lipid liposomes. Full-length gels are presented in Supplementary Figure S1.
