FIG. 7.

(A) Diagram of the domain organization of the fxbB and fxbC products. White boxes indicate the amino acid activating domains. Each activating domain has an ATP-binding site, an ATPase motif, and a pantetheine motif (Pan- Site) and is separated by space motifs. B1 and B2 are the two amino acid activating domains in FxbB; C1, C2, C3, and C4 are the four amino acid activating domains in FxbC. There is one epimerase domain in FxbB and two epimerase domains in FxbC. The Tn10 insertion site in pYUB908 and mc²1608 and the Tn10 insertion site in pYUB909 and mc²1609 are indicated by superscript letters a and b, respectively. (B) Covalent structure of M. smegmatis exochelin (40).