Mediator Structural Conservation and Implications for the Regulation Mechanism

Gang Cai; Tsuyoshi Imasaki; Yuichiro Takagi; Francisco J. Asturias

doi:10.1016/j.str.2009.01.016

Figure 2

An external file that holds a picture, illustration, etc.
Object name is nihms100261f2.jpg

Yeast Mediator conformational variability and Cryo-EM reconstruction

(A) A selection of class averages obtained by statistical classification of images of Mediator particles preserved in stain showing variability in the position of the Head domain (labeled H in the top middle average) and the top of the Tail domain (labeled T in the top middle average). The number of images included in each class average is indicated by the number under each average. (B) Initial models for alignment of cryo-images by projection matching were generated by filtering a previous stain reconstruction of Mediator to ~10 nm and computationally varying the position of the Head domain (as indicated by the red outline). (C) Cryo-EM reconstruction of yeast Mediator calculated from images of ~9,000 particles carefully selected based on their conformational homogeneity. Curved black arrows in the Front view indicate the approximate magnitude and direction of variability in the position of the Head and middle portions of the structure. Apparent multiplicity of the top portion of the Tail domain results from significant mobility. Red stars identify a portion of the density that seems to correspond best to the shape and most common position of the tip of the Tail domain.