FIG. 4.

Variety of mechanisms used in regulating methionine and serine biosynthetic genes of B. subtilis and other bacteria. The regulatory mechanisms and operon arrangements found in B. subtilis (left column) are compared with those of T-box-regulated operons in other members of the Firmicutes (right column). Where genes of other organisms share the same regulatory mechanism as B. subtilis, the names of these organisms are indicated in the B. subtilis column. The graphic representation of each type of regulatory element is indicated in the red box in each subfigure. No attempt was made to identify pathways exhibiting feedback inhibition of enzyme activity; only those reported in the literature for B. subtilis are indicated. The regulatory proteins shown represent their corresponding binding sites in the operon. Genes that have not been annotated were labeled based on their corresponding COG numbers (i.e., a gene that belongs to COG1878 is drawn as an arrow containing the number “1878”). Organism abbreviations and color codes are described in the legends of Fig. 2 and 3.