Garcia-Bernardo J, Braña A F, Méndez C, Salas J A
Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A), Universidad de Oviedo, 33006, Oviedo, Spain.
FEMS Microbiol Lett. 2000 May 1;186(1):61-5. doi: 10.1111/j.1574-6968.2000.tb09082.x.
Mithramycin is an antitumor aromatic polyketide synthesized by Streptomyces argillaceus. Two genes (mtrX and mtrY) of the mithramycin gene cluster were inactivated by gene replacement. Inactivation of mtrX, that encodes an ABC excision nuclease system for DNA repair, produced a mutant that was affected in the normal rate of growth. Expression of mtrX in Streptomyces albus in a multicopy plasmid vector conferred a low increase in resistance to mithramycin. Inactivation of mtrY, that encodes a protein of unknown function, produced a 50% decrease in mithramycin biosynthesis. When mtrY was expressed in the wild-type S. argillaceus in a multicopy plasmid, this caused about 47% increase in the levels of mithramycin production. It is proposed that mtrX and mtrY could code for a secondary defense mechanism and a mithramycin regulatory element, respectively.
光神霉素是由泥质链霉菌合成的一种抗肿瘤芳香聚酮化合物。通过基因置换使光神霉素基因簇的两个基因（mtrX和mtrY）失活。编码用于DNA修复的ABC切除核酸酶系统的mtrX失活产生了一个生长速率受到影响的突变体。在多拷贝质粒载体中白链霉菌中mtrX的表达使对光神霉素的抗性略有增加。编码功能未知蛋白质的mtrY失活导致光神霉素生物合成减少50%。当mtrY在多拷贝质粒中在野生型泥质链霉菌中表达时，这导致光神霉素产量水平增加约47%。有人提出，mtrX和mtrY可能分别编码一种二级防御机制和一个光神霉素调节元件。
