Polynucleotides, such as DNA, are provided which accelerate the biosynthesis of a HMG-CoA reductase inhibitor, ML-236B, in an ML-236B producing micro-organism when introduced in the ML-236B producing micro-organism. Pravastatin, which is an HM-CoA reductase inhibitor, can be obtained using Streptomyces carbophilus by microbial conversion of ML-236B produced by Pencillium citrinum. The polynucleotides encode a gene (such as micA (polyketide synthase), mlcB (polyketide synthase), micE (efflux pump) or mlcR (transcription factor). Provided are vectors into which such polynucleotides are incorporated; host cells transformed by such vectors; and proteins expressed by such vectors. A method for producing ML-236B using such polynucleotides and/or proteins which comprises recovering ML-236B from a culture of the host cell.