Isolation and structure of mycobactin T, a growth factor from Mycobacterium tuberculosis

Abstract

A growth factor for Mycobacterium johnei isolated from M. tuberculosis as an Fe complex was named ferric mycobactin-T. Ferric mycobactin-T is a mixture of at least 4 closely related components differing only in their fatty-acid side chains. Mycobactin-T resembles mycobactin-1 P in structure but differs in the following respects: the aromatic acid residue is salicylic acid in place of 2-hydroxy-6-methylbenzoic acid; the hydroxy acid residue is (+)-[beta]-hydroxybutyric acid in place of (-)-3-hydroxy-2-methyl-pentanoic acid; its components have fatty-acid side chains that are mostly different from the side chains of the components in mycobactin-P preparations. One minor component in mycobactin-T probably has a cis-octadec-2-enoyl side chain. The major side-chain components correspond to acids of chain length C18-C21 that are not n-saturated or n-delta2-unsaturated acids. The differences in biosynthesis between mycobactins-T and -P are discussed.