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Sulfation and amidinohydrolysis in the biosynthesis of giant linear polyenes

Clethramycin from DSM4137, and mediomycins (produced together with clethramycin from ), are near-identical giant linear polyenes apparently constructed from, respectively, a 4-guanidinobutanoate or 4-aminobutanoate starter unit and 27 polyketide extender units, and bearing a specific -sulfonate modi...

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Published in:Beilstein journal of organic chemistry 2017-11, Vol.13 (1), p.2408-2415
Main Authors: Hong, Hui, Samborskyy, Markiyan, Usachova, Katsiaryna, Schnatz, Katharina, Leadlay, Peter F
Format: Article
Language:English
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Summary:Clethramycin from DSM4137, and mediomycins (produced together with clethramycin from ), are near-identical giant linear polyenes apparently constructed from, respectively, a 4-guanidinobutanoate or 4-aminobutanoate starter unit and 27 polyketide extender units, and bearing a specific -sulfonate modification at the C-29 hydroxy group. We show here that mediomycins are actually biosynthesised not by use of a different starter unit but by direct late-stage deamidination of (desulfo)clethramycin. A gene ( ) encoding a candidate sulfotransferase has been located in both gene clusters. Deletion of this gene in DSM4137 led to accumulation of desulfoclethramycin only, instead of a mixture of desulfoclethramycin and clethramycin. The mediomycin gene cluster does not encode an amidinohydrolase, but when three candidate amidinohydrolase genes from elsewhere in the genome were individually expressed in and assayed, only one of them ( ), located 670 kbp away from the mediomycin gene cluster on the chromosome, catalysed the removal of the amidino group from desulfoclethramycin. Subsequent cloning of into DSM4137 caused mediomycins A and B to accumulate at the expense of clethramycin and desulfoclethramycin, respectively, a rare case where an essential biosynthetic gene is not co-located with other pathway genes. Clearly, both desulfoclethramycin and clethramycin are substrates for this amidinohydrolase. Also, purified recombinant sulfotransferase from DSM4137, in the presence of 3'-phosphoadenosine-5'-phosphosulfate as donor, efficiently converted mediomycin B to mediomycin A in vitro. Thus, in the final steps of mediomycin A biosynthesis deamidination and sulfotransfer can take place in either order.
ISSN:1860-5397
2195-951X
1860-5397
DOI:10.3762/bjoc.13.238