Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of radicicol, a resorcylic acid lactone (RAL) that irreversibly inhibits the HSP90 molecular chaperone, an important target for cancer chemotherapy (PubMed:19101477). The cluster encodes only two apparent post-PKS enzymes, a cytochrome P450 monooxygenase (radP) and a non-heme halogenase (radH) that introduce the epoxide and the chlorine, respectively (PubMed:19101477). If this cluster includes all the genes required for radicicol biosynthesis, the remaining structural features of radicicol are presumably generated by the PKSs rads1 and rads2 (PubMed:19101477). The C-2' ketone could arise if the R-PKS rads1 and NR-PKS rads2 each carry out four iterations, in contrast to the five iteration-three iteration split for the hypothemycin PKSs (By similarity). The origin of the cis 5',6' double bond is not known (By similarity). The radicicol R-PKS rads1 ER domain may catalyze either double bond isomerization or reduction in the third iteration (By similarity). Secondary metabolite biosynthesis. Multidomain protein; including a starter unit:ACP transacylase (SAT) that selects the starter unit; a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a product template (PT) domain that controls the immediate cyclization regioselectivity of the reactive polyketide backbone; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm (By similarity). The release of the polyketide chain from the non-reducing polyketide synthase is mediated by the thioesterase (TE) domain localized at the C-ter of the protein (By similarity). Completely abolishes the production of radicicol (PubMed:19101477). Radicicol is an important pharmacophore as an inhibitor of heat shock protein 90 (Hsp90), an ATP-dependent chaperone involved in the post-translational maturation and stabilization of over one hundred proteins, and which activity has been implicated in diverse pathologies ranging from oncology to neurodegenerative and infectious diseases (PubMed:19101477).