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. 2007 Mar 16;35(7):2227–2237. doi: 10.1093/nar/gkm045

Figure 1.

Figure 1.

Schematic diagram of shared secondary structure elements observed after a structural alignment of Type II REases. Triangles represent β-strands and circles represent the α-helices. Up and down triangles are used to indicate the direction of one β-strand with respect to another. The letters S and H followed by a digit label the β-strands and α-helices, respectively, according to their position. Elements are colored using a scale in which those that appear with higher frequency in the structures of the 22 proteins are shown in longer wavelength colors. The red triangles designate the strands that are common to all Type II REase structures. The frequency of appearance of each secondary structure element is the following: H1 = 22/22; H2 = 20/22, H3 = 20/22, H4 = 16/22, S-3 = 1/22, S-2 = 1/22, S-1 = 2/22, S1 = 22/22, S2 = 22/22, S3 = 22/22, S4 = 22/22, S5 = 22/22 (with S5 parallel to S1 or S5up = 14/22, and S5 anti parallel to S1 or S5down = 8/22) and S6 = 13/22 (with S6 parallel to S1 or S6up = 9/13, and S6 anti parallel to S1 or S6down = 4/13).