Overexpression of Bro1 or the Bro1 domain stabilizes ESCRT-III polymers at endosomes. (A) Western blot analysis of detergent-solubilized yeast membranes resolved by isopycnic density gradient centrifugation. Inclusion of 1% Triton X-100 throughout the gradients yielded identical sedimentation profiles. (B) Quantitation of triplicate gradients from A.