%0 Journal Article %A Menéndez, Nuria %A Braña, Alfredo F. %A Salas, José A. %A Méndez, Carmen %T Involvement of a chromomycin ABC transporter system in secretion of a deacetylated precursor during chromomycin biosynthesis %D 2007 %J Microbiology, %V 153 %N 9 %P 3061-3070 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.2007/007922-0 %K ABC, ATP-binding cassette %K DDACA3, 4A,4E-O-dideacetyl-chromomycin A3 %I Microbiology Society, %X Chromomycin A3 is an antitumour antibiotic that acts by inhibiting transcription and replication of DNA. The producer micro-organism Streptomyces griseus subsp. griseus is highly resistant to chromomycin A3 and to the structurally related compound mithramycin upon induction with chromomycin A3. The biosynthetic gene cluster of chromomycin contains three genes involved in self-resistance to chromomycin in S. griseus: cmrA and cmrB encode a type I ATP-binding cassette (ABC) transporter, and cmrX encodes a UvrA-like protein of ABC excision nuclease systems. These genes are linked in the chromosome, together with a gene encoding a transcriptional repressor (cmmRII). Involvement of these genes in chromomycin resistance was determined through gene inactivation, and heterologous expression in Streptomyces albus. Inactivation of cmrX produced a chromomycin-sensitive low-producer strain, while inactivation of cmmRII generated a high-chromomycin-producer strain, which was resistant to chromomycin, and also to mithramycin. Expression of either cmrA and cmrB, or cmrX, in S. albus generated strains with low chromomycin resistance; it was therefore necessary to co-express the three genes to achieve high levels of resistance. However, the CmrAB ABC transporter conferred a high level of resistance to the biosynthesis intermediate 4A,4E-O-dideacetyl-chromomycin A3. A model is proposed for the biosynthesis of, and self-resistance to, chromomycin A3 in S. griseus subsp. griseus. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.2007/007922-0