Fig. 6: 3D variability analysis from the short CDTa-bound CDTb-pore.

a Flow chart of cryo-EM image processing with 3D variability analysis. The short CDTa-bound CDTb-pore particles were classified into the folded CDTa class and the unfolded CDTa class, followed by 3D refinement respectively. More detailed information is described in result and method. b The density map of the folded CDTa class. c FSC curve of the half maps and FSC curve for cross-validation between the map and model of folded CDTa class. d The density map of the unfolded CDTa class. e FSC curve of the half maps and FSC curve for cross-validation between the map and model of unfolded CDTa class. f, g Density map of CDTa (folded or unfolded) and the surface model of subunit C and F of CDTb-pore. The map of CDTa was colored as N-terminal helices (red), N-terminal domain (yellow) and C-terminal domain (purple), respectively. The constrictions designated Ca-edge, NSS-loops and ϕ-clamp are shown in blue, cyan, and purple, respectively. h, i The model of the CDTa (folded or unfolded) N-terminus and the NSS-loops. The blue NSS-loops indicate ‘in’ state, and the yellow NSS-loops indicate ‘out’ state.