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Proposed arrangement of proteins forming a bacterial type II polyketide synthase

Aklanonic acid is synthesised on a type II polyketide synthase (PKS) composed of 8 proteins that catalyze the condensation between a propionate starter unit and 9 malonate extender units. We have investigated the network of protein interactions within this complex using a yeast two hybrid system, coaffinity chromatography and by computer aided protein docking simulations. Our results suggest that the ketosynthase (KS) α and β subunits interact with each other and that the KSα subunit (DpsA) also probably interacts with a malonyl-CoA: ACP acyltransferase (DpsD) forming a putative minimal synthase. We speculate that DpsD may physically inhibit the priming reaction allowing the choice of propionate rather than acetate as the starter unit. We also suggest a structural role for the cyclase (DpsY) maintaining the overall structural integrity of the complex.

aklanonic acid; daunorubicin; doxorubicin; type II polyketide synthase; protein structure

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