( ting components of green tea red wine...)When the going gets tough, slime molds start synthesizing

Turns out, DIF-1 belongs to the same crowd. "While reading a review article on the diversity of polyketides in the journal Nature, we realized that the core chemical structure of DIF-1, an important developmental signal in Dictyostelium, is similar to natural products made by plant type III PKSs," recalls Austin.

At the time, Dictyostelium was in the midst of having its genome sequenced, and the bits and pieces of raw DNA sequencing data were being deposited in publicly available databases. Austin recalled, "One night I performed a bioinformatics search to look for genetic evidence that would suggest the existence of a type III PKS in Dictyostelium." Using various computer programs to find, assemble, and translate in silico the relevant raw DNA sequencing fragments first into genes then into the proteins these genes encode, Austin reconstructed two type III PKS-like gene sequences, and also found a surprise.

Unexpectedly, these deduced genetic blueprints for type III PKSs revealed each Dictyostelium type III PKS to be fused to other enzymatically active protein domains. This never seen before hybrid arrangement works like a very efficient bucket brigade that synthesizes polyketide molecules in slime mold cells.

"Nature has paved the way to exploit this novel domain arrangement to bioengineer more efficient ways of making modified polyketides for human uses," said Austin.

Moving to the bench, Austin and Noel lab manager Marianne Bowman isolated Dictyostelium DNA encoding the type III PKS domains and not only determined their structure, which indeed resembled a plant PKS, but also showed that one of them, called Steely2, made the chemical scaffold of DIF-1 in a test tube. All that was left was to prove was that slime molds themselves used the newly discovered enzyme to make DIF-1.

For that Noel and Austin turned to co-senior author Robert Kay, Ph.D., a Dicty
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Source:Salk Institute