The biosynthesis of differentiation-inducing factor, a chlorinated signal molecule regulating Dictyostelium development.
Differentiation-inducing factor (DIF)-1 is a chlorinated alkyl phenone released by developing Dictyostelium amoebae, which induces them to differentiate into stalk cells. A biosynthetic pathway for DIF-1 is proposed from labeling, inhibitor, and enzymological experiments. Cells incorporate 36Cl- into DIF-1 during development, showing that the chlorine atoms originate from chloride ions; peak incorporation is at the first finger stage. DIF-1 synthesis can be blocked by cerulenin, a polyketide synthase inhibitor, suggesting that it is made from a polyketide. This is most likely the C12 polyketide (2,4,6-trihydroxyphenyl)-1-hexan-1-one (THPH). Feeding experiments confirm that living cells can convert THPH to DIF-1. Conversion requires both chlorination and methylation of THPH, and enzymatic activities able to do this exist in cell lysates. The chlorinating activity, assayed using 36Cl-, is stimulated by H2O2 and requires both soluble and particulate components. It is specific for THPH and does not use this compound after O-methylation. The methyltransferase is soluble, uses S-adenosyl-L-methionine as a co-substrate, has a Km for dichloro-THPH of about 1.1 microM, and strongly prefers this substrate to close analogues. Both chlorinating and methyltransferase activities increase in development in parallel with DIF-1 production, and both are greatly reduced in a mutant strain that makes little DIF-1. It is proposed that DIF-1 is made by the initial assembly of a C12 polyketide skeleton, which is then chlorinated and methylated.
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Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, United Kingdom.
D000818:Animals; D002454:Cell Differentiation; D002569:Cerulenin / Q000494:pharmacology; D002711:Chloride Peroxidase / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D004023:Dictyostelium / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D006588:Hexanones / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D008956:Models, Chemical; D010636:Phenols / Q000378:metabolism*; D015398:Signal Transduction; D013379:Substrate Specificity
C110391:(2,4,6-trihydroxyphenyl)-1-hexan-1-one; D002712:Chlorides; D006588:Hexanones; D010636:Phenols; C053433:1-((3,5-dichloro)-2,6-dihydroxy-4-methoxyphenyl)-1-hexanone; D002569:Cerulenin; D002711:Chloride Peroxidase; D008780:Methyltransferases