Limited regulation aspects of rapamycin and FK520 biosynthesis have been studied in recent years [20–23]. Two regulatory genes, rapH and rapG, were identified in the rapamycin biosynthetic cluster and their role in regulation of rapamycin biosynthesis was confirmed [20]. Rapamycin RapH and its homologue in the FK520 biosynthetic cluster FkbN both belong to the LAL family of transcriptional regulators [16, 24] since they both contain a LuxR-type helix-turn-helix (HTH) DNA binding motif at the C terminus 4SC-202 purchase [25] and an ATP-binding site at the N terminus [26]. In addition to fkbN, the gene cluster for FK520 biosynthesis

from Streptomyces hygroscopicus var. ascomyceticus also contains a second regulatory gene, termed fkbR1, belonging to the LysR-type transcriptional regulators (LTTR) [21]. Until recently, regulatory genes have not been systematically investigated in FK506-producing strains. In the course of our recent work on FK506 biosynthesis [12, 27] we have obtained a complete sequence of the FK506 biosynthetic cluster from Streptomyces tsukubaensis NRRL 18488.

The obtained sequence allowed us to compare the putative regulatory elements present in our sequence with the other three FK506 gene clusters [11]. In addition, we have evaluated the role of three putative regulatory APR-246 genes in the FK506 biosynthetic cluster using gene inactivation and over-expression approaches, as well as studied the transcription of FK506 biosynthetic genes in the mutant strains. In this work, we have demonstrated, that the biosynthesis of the FK506 ID-8 in Streptomyces tsukubaensis NRRL 18488 is regulated by two positively-acting regulatory proteins, and remarkably, compared to the apparently closely-related strain, Streptomyces

sp. KCTC 11604BP [28], it differs substantially. Methods Bacterial strains and culture conditions We based our studies on Streptomyces tsukubaensis NRRL 18488 strain [12], a wild type progenitor of the industrially used FK506 high-producing strains. For spore stock preparation S. tsukubaensis strains were cultivated as a confluent lawn on the ISP4 agar sporulation medium [29] for 8–14 days at 28°C. For GSK2126458 molecular weight liquid cultures spores of S. tsukubaensis strains were inoculated in seed medium VG3 (0.25% (w/v) soy meal, 1% dextrin, 0.1% glucose, 0.5% yeast extract, 0.7% casein hydrolyzate, 0.02% K2HPO4, 0.05% NaCl, 0.0005% MnCl2 × 4H2O, 0.0025% FeSO4 × 7H2O, 0.0001% ZnSO4 × 7H2O, 0.0005% MgSO4 × 7H2O, 0.002% CaCl2, pH 7.0) and incubated at 28°C and 250 rpm for 24–48h. 10% (v/v) of the above seed culture was used for the inoculation of production medium PG3 (9% dextrin, 0.5% glucose, 1% soy meal, 1% soy peptone, 1% glycerol, 0.25%. L-lysine, 0.1% K2HPO4, 0.15% CaCO3, 0.1% polyethylene glycol 1000, pH 6.5) [12, 29]. Cultivation was carried out at 28°C, 250 rpm for 6–7 days.