Fig. 4.

Evolutional conservation of the catalytic residues in transcript-cleavage factors. (A) Sequence alignment of Gre factors. D41 and E44 residues are marked (19). (B) Structure of TFIIS factor. Cyan, β-strands; gray, loops. Functionally important residues (Asp-261 and Glu-262) are shown in ball-and-stick representation and highlighted. The atomic coordinates were taken from Protein Data Bank (PDB ID code 1TFI). Sequence alignment for the residues constituting the tip of the functionally important loop of the factor is presented.