Polypeptides involved in the biosynthesis of streptogramins, nucleotide sequences coding for these polypeptides and their use

A method for preparing pristinamycin IIA or IIB comprising:

• a) specifically introducing a disabling mutation into at least one gene target in a microorganism that produces pristinamycin IA and pristinamycin IB, wherein said gene target is selected from the snbA gene of SEQ ID NO:
• 5 and genes that hybridize to the snbA gene of SEQ ID NO:
• 5 of Streptomyces pristinaespiralis in the presence of formamide at 42° C. with washes at 50° C. and 60° C. in 2×SCC and 0.1% SDS, wherein said gene target encodes a polypeptide that is a 3-hydroxypicolinic acid:adenosine 5′-monopiosphate ligase;
• (b) selecting cells containing the mutated gene, wherein the cells are blocked in the production of pristinamycin IA and IB;
• (c) culturing said cells;
• and
• (d) recovering said pristinamycin IIA, pristinamycin IIB, or pristinamycin IIA and IIB.