FIG. 5.

Structural models for σ³² residues 264 to 283 of region 4.2 (A) and for residues 88 to 120 of regions 2.2 to 2.4 (B). These models were rendered using DeepView-Swiss PDB Viewer version 3.7 by superimposing the sequences of E. coli σ³² onto the experimentally determined structures of T. aquaticus σ^A (3), as indicated on the figures. The justification for this simplified approach is derived from the observation that structure is remarkably well conserved among the σ⁷⁰-like sigma factors. The side chains for which substitutions were introduced are colored red, and other residues are blue. The protein backbone is green, and for α-helices it is shown as a green ribbon.