Negative-stain EM 2D class averages of LRP1 and LRP1-RAP complex. The averaged 10 most populated classes with the highest signal-to-noise ratio of a total of ∼2,000 particles manually picked for each sample preparation are shown. The box size is 62 nm2. A, LRP1 after gel filtration at pH 7.5. B, co-expressed LRP1-RAP complex after gel filtration at pH 7.5. C, LRP1 after gel filtration at pH 5.5. D, co-expressed LRP1-RAP after gel filtration at pH 5.5 and dissociation of RAP.