IS1136, an insertion element in the erythromycin gene cluster of Saccharopolyspora erythraea

The Saccharopolyspora erythraea eryAI and eryAII genes, which, together with eryAIII, are responsible for the formation of the macrolactone portion of the antibiotic erythromycin, are separated by a 1.46-kb segment, designated IS1136, with the characteristics of an insertion sequence. It contains an open reading frame of 425 codons similar to that of the Anabaena IS891 and is present in four nonidentical copies in the Sac. erythraea genome. Inverted repeats were found near the ends of IS1136, and in the copy in eryA, one of the ends was found to overlap the 5' end of eryAII. Hybridization analysis suggests that IS1136 is confined to Saccharopolyspora species containing eryA-homologous DNA.