[Functional characterization of gouC and gouD in gougerotin biosynthesis].

Objective: To determine the functions of gouC and gouD in gougerotin biosynthesis, disruption of these two genes was performed. As gougerotin producing strain Streptomyces graminearus lacks efficient genetic manipulation system, the gene cluster for gougerotin biosynthesis was heterologously expressed in Streptomyces coelicolor M1146 to facilitate genetic manipulations of gouC and gouD.

Methods: By using fosmid D6-4H containing the complete gougerotin biosynthetic gene cluster, gouC and gouD were disrupted by PCR-targeting method to generate pGOUe-ΔC and pGOUe-ΔD. Both pGOUe-ΔC and pGOUe-ΔD were introduced into Streptomyces coelicolor M1146 by intergeneric conjugation, thus gouC and gouD disrpution mutants (Ml146-GOUe-AC and M1146-GOUe-ΔD) were obtained. The gougerotin production of M1146-GOUe-ΔC and M1146-GOUe-ΔD were assayed by HPLC analysis. The intermediates accumulated in these mutants were purified and subjected to MS and NMR analyses for structure determinations. Bioassay of these intermediates against tumor cell line were also carried out.

Results: Disruption mutants of gouC and gouD failed to produce gougerotin and the mutants accumulated different gougerotin intermediates, which lost their ability to inhibit cancer cell proliferation.

Conclusion: gouC and gouD are key structual genes in the biosynthesis of gougerotin peptidyl moieties. This study will pave the way for the elucidation of gougerotin biosynthetic pathway.