Summary: Production of the red antibiotic, undecylprodigiosin, by A3(2) was studied by DNA cloning and biochemical analysis. Over 21 kb of genomic DNA were cloned, in several segments, into plasmid vectors. The cloned DNA ‘complemented’ several specific mutations in the gene cluster. Four genes (, and ) were mapped to different regions within the cloned DNA. Screening with probes for DNA homologies among various streptomycetes revealed hybridizing DNA in three strains, one of them not known to synthesize prodigiosin pigments. Biochemical studies using protoplasted cells revised our interpretation of the nature of and mutations. Two forms of undecylnorprodigiosin:-adenosylmethionine -methyltransferase activity on gel filtration columns were detected: a very high molecular mass peak (>5 MDal) and a 49 kDal peak. Analyses of extracts from mutants suggested that these two forms are related, and that at least the and gene products are necessary for -methyltransferase activity Lack of activity of the gene in a heterologous host, , is consistent with the necessity for a biosynthetic complex involving several gene products for efficient expression. Experiments in liquid antibiotic production medium indicated that prodigiosin compounds in are examples of ‘secondary metabolites’ whose synthesis lags behind that of cell mass. The peak of specific activity of -methyltransferase coincided with the ‘late exponential’ phase of growth. Thus, understanding the genetic regulation of undecylprodigiosin biosynthesis in may be relevant to other antibiotic production pathways, and perhaps to ‘secondary’ metabolism in general.


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