n. [ From actinomyces, the genus of the organism in which they were first found. ] 1. any of various red antibiotics isolated from soil bacteria with a three-ring heterocyclic nucleus with an attached peptide chain. Actinomycin D is the most well-known and has been used to treat certain tumors. They act by binding to DNA and inhibiting the transcription of RNA. Their binding to DNA has been much studied.
Syn. -- actinomycin actinomycin C actinomycin F1 actinomycin D [ WordNet 1.5 ]

n. [ From actinomyces, the genus of the organism in which they were first found. ] The most well-known of the actinomycins (C62H86N12O16), a class of antibiotics which act by binding to DNA and inhibiting synthesis of RNA; they act agains gram-positive bacteria and many eukaryotic organisma. Actinomycin D has been used in human medicine to treat certain tumors.
Syn. -- dactinomycin, actinomycin IV, Cosmegen[ trade name ], actinomycin C1, actinomycin I1 [ PJC ]