posted on 2019-07-23, 18:39authored byLiao-Bin Dong, Yu-Chen Liu, Alexis J. Cepeda, Edward Kalkreuter, Ming-Rong Deng, Jeffrey D. Rudolf, Changsoo Chang, Andrzej Joachimiak, George N. Phillips, Ben Shen
Nonheme diiron monooxygenases make
up a rapidly growing family
of oxygenases that are rarely identified in secondary metabolism.
Herein, we report the in vivo, in vitro, and structural characterizations
of a nonheme diiron monooxygenase, PtmU3, that installs a C-5 β-hydroxyl
group in the unified biosynthesis of platensimycin and platencin,
two highly functionalized diterpenoids that act as potent and selective
inhibitors of bacterial and mammalian fatty acid synthases. This hydroxylation
sets the stage for the subsequent A-ring cleavage step key to the
unique diterpene-derived scaffolds of platensimycin and platencin.
PtmU3 adopts an unprecedented triosephosphate isomerase (TIM) barrel
structural fold for this class of enzymes and possesses a noncanonical
diiron active site architecture with a saturated six-coordinate iron
center lacking a μ-oxo bridge. This study reveals the first
member of a previously unidentified superfamily of TIM-barrel-fold
enzymes for metal-dependent dioxygen activation, with the majority
predicted to act on CoA-linked substrates, thus expanding our knowledge
of nature’s repertoire of nonheme diiron monooxygenases and
TIM-barrel-fold enzymes.