Fig. 4. Principal component analysis of the mtSSU head motion suggests a function for the mitoribosomal protein mS37 in restricting the swiveling.

a–c The relative orientation of the head to the body is described by 12 eigenvectors, representing translation and rotation in each particle. The eigenvectors 1, 2, and 3 were found to mainly contribute to the head motion, as indicated. d Histogram of the variances explained by the 12 eigenvectors. e, f The 1st to 3rd eigenvalues of randomly chosen particles represented by dots are plotted against each other, showing non-gaussian distribution for the swiveling motion. The particles are classified based on the values of eigenvector 1 (rectangles). g, h Comparison between the reconstructions of the classified particles. The closed conformation (Class 1) exhibits weaker density for the mtIF3-NTD interacting with mS37 and uS7m, compared to the other conformations with higher particle numbers.