FIG. 2.
Actinomycin biosynthetic gene cluster. The functions of the 28 genes that make up the gene cluster, including the 4 already known NRPS genes acmA to -D (66), are represented by arrows as follows: black, regulation; dark gray, 4-MHA biosynthesis; white, unknown role or function; gray, NRPS genes. In the lower part is shown the assembly line of the four NRPS subunits which catalyze the formation of 4-MHA pentapeptide lactone.