FIG. 5.

Comparison of the amino acid sequences in the region 2.5 of the sigma factors of M. smegmatis (ς^A and ς^B) and the principal sigma factor of E. coli (RpoD). The two amino acids previously implicated in making specific contacts with the TGN motif (filled circles), identical amino acids (dashes), conserved substitutions (plain letters), and nonconserved substitutions (boldfaced letters) are indicated. The amino acid sequences are from reference 17 for RpoD of E. coli and from reference 24 for ς^A and ς^B of M. smegmatis. The consensus sequence is from reference 4, wherein the amino acids that exhibit a high-frequency occurrence (based on a compilation of 30 sigma factors) are indicated. Conserved substitutions are defined as the following groups: I, L, M, and V; A and G; S and T; K, H, and R; D, E, N, and Q; F, Y, and W; C; and P. The numbers do not represent actual amino acid positions.