Electrons and X-rays gang up on the ribosome Christopher Davies, Stephen W White  Structure  Volume 8, Issue 3, Pages R41-R45 (March 2000) DOI: 10.1016/S0969-2126(00)00111-8

Figure 1 A simplified diagram of the ribosomal elongation cycle showing the participation of elongation factors EF-Tu (orange rectangle) and EF-G (purple oval). Amino acids are shown as coloured circles, and their associated tRNA molecules as elongated rectangles of the same colour. The ribosome is divided into a large (upper) subunit and a small (lower) subunit, and the tRNA molecules can occupy three sites, A, P and E, that span the subunit interface. The mRNA (thick horizontal line) is bound to the small subunit. Proposed relative movements of the subunits during elongation are indicated. Progress of the elongation cycle requires conformational changes in both EF-Tu and EF-G (indicated by the altered shapes of the rectangle and oval, respectively). These conformational changes are driven by the turnover of GTP. (The figure was adapted from [28].) Structure 2000 8, R41-R45DOI: (10.1016/S0969-2126(00)00111-8)

Figure 2 A direct comparison of the latest images of the ribosome obtained by X-ray crystallography (left) and electron microscopy (EM; right). In each case, the pairwise views are in equivalent orientations showing the subunit interface surface. (a) The isolated small (30S) subunit. The X-ray image (5.5 Å) is reproduced from [20] with permission. The EM image was obtained by a separation of the latest 11.5 Å map of the complete E. coli 70S ribosome from the Frank group [29]. The decoding site is located at the top of a distinctive vertical extended region of double-stranded RNA that is depicted in a paler yellow on the EM map (see also (c) below). (b) The isolated large (50S) subunit. The X-ray image (5 Å) is reproduced from [22] with permission, and the EM image (7.5 Å) is reproduced from [3]. Note that, in the X-ray image, the L1 stalk (on the left hand side) is missing, but it is clearly visible in the EM image. (c) The 30S subunit and (d) the 50S subunit in the context of the 70S ribosome with the three tRNA molecules included. The X-ray images (7.8 Å) were reproduced from [23] with permission, and the EM images were obtained by a separation of Frank's 11.5 Å map (see above). In the X-ray images, the A, P and E site tRNAs are shown in green, blue and orange, respectively. In the EM images, the A, P and E sites are in purple, green and orange, respectively, and are inferred from previous EM studies [11,14]. Note that the agreement between the positions of the tRNA molecules in both images is excellent. Also, the A and P site tRNAs are adjacent, whereas the E site tRNA is further away. Structure 2000 8, R41-R45DOI: (10.1016/S0969-2126(00)00111-8)