Figure 4.

Distribution of FAS conformations is altered in the presence of substrates. (a) The Δ22-FAS and H878A (DH) mutants were imaged without substrates and these mutants and the C161Q (KS) mutant were imaged in the presence of substrates. Particles from all five data sets were classified together into 50 groups. After discarding 6 classes of grossly misaligned or distorted particles (3.4% of particles, not shown), the remaining 44 classes were categorized into those with symmetric (red) and asymmetric (blue) conformations in the upper β-carbon processing section (Top conformation) and those with perpendicular (faded colors) or in-plane conformations in the lower MAT-KS₂-MAT section (Bottom conformation). The in-plane conformations exhibited by the lower section are arranged according to the degree of rotation of the lower section: from left-swinging (Left closed) to right-swinging (Right closed). For simplicity, class averages that show an opening between the DH, ER, and KR domains in the left half of the structure were mirrored so that the opening always appears in the right half of the structure. (b) Cartoon representation of each conformation colored according to a. (c) After categorization of classes, the numbers of particles from each FAS preparation in each category were determined. Bars are colored according to conformations as in a and b.