2000 Volume 53 Issue 2 Pages 144-152
The actVI genetic region of Streptomyces coelicolor A3 (2) is part of the biosynthetic gene cluster of actinorhodin (ACT), the act cluster, consisting of six ORFs: ORFB, ORFA, ORF1, ORF2, ORF3, ORF4. A newly devised method of ACT detection with a combination of HPLC and LC/MS was applied to the analysis of the disruptants of each ORE ACT was produced by those of ORFB, ORFA, ORF3, and ORF4. Instead of ACT, the ORF1 disruptant produced 3, 8-dihydroxy-1-methylanthraquinone-2-carboxylic acid (DMAC) and aloesaponarin II as shunt products. The ORF2 disruptant gave 4-dihydro-9-hydroxy-1 -methyl- 10-oxo-3-H-naphtho-[2, 3-c]-pyran-3-(S)-acetic acid, (S)-DNPA. These results support our previous proposal for stereospecific pyran ring formation in the biosynthesis of ACT, most importantly suggesting that the actVI-ORF2 product would recognize (S)-DNPA as a substrate for stereospecific reduction at C-15. The disruptant of ORFA produced (S)-DNPA together with ACT, suggesting that actVI-ORFA might play a role such as stabilising the multicomponent, type II PKS complex.
