Butenyl-spinosyns, a natural example of genetic engineering of antibiotic biosynthetic genes

• DOI: 10.1007/s10295-005-0016-9
• Publication Date: 2005-09-22T14:45:01Z
• Authors: Donald R. Hahn; Gary Gustafson; Clive Waldron; Brian Bullard; James D. Jackson; Jon Mitchell
• Keywords: 0301 basic medicine; Base Sequence; Molecular Sequence Data; Sequence Analysis, DNA; Cosmids; Anti-Bacterial Agents; 03 medical and health sciences; Bacterial Proteins; Macrolides; Genetic Engineering; Polyketide Synthases; Gene Deletion; Gene Library; Saccharopolyspora

Spinosyns, a novel class of insect active macrolides produced by Saccharopolyspora spinosa, are used for insect control in a number of commercial crops. Recently, a new class of spinosyns was discovered from S. pogona NRRL 30141. The butenyl-spinosyns, also called pogonins, are very similar to spinosyns, differing in the length of the side chain at C-21 and in the variety of novel minor factors. The butenyl-spinosyn biosynthetic genes (bus) were cloned on four cosmids covering a contiguous 110-kb region of the NRRL 30141 chromosome. Their function in butenyl-spinosyn biosynthesis was confirmed by a loss-of-function deletion, and subsequent complementation by cloned genes. The coding sequences of the butenyl-spinosyn biosynthetic genes and the spinosyn biosynthetic genes from S. spinosa were highly conserved. In particular, the PKS-coding genes from S. spinosa and S. pogona have 91-94% nucleic acid identity, with one notable exception. The butenyl-spinosyn gene sequence codes for one additional PKS module, which is responsible for the additional two carbons in the C-21 tail. The DNA sequence of spinosyn genes in this region suggested that the S. spinosa spnA gene could have been the result of an in-frame deletion of the S. pogona busA gene. Therefore, the butenyl-spinosyn genes represent the putative parental gene structure that was naturally engineered by deletion to create the spinosyn genes.