1 research outputs found
Crystal Structures of SgcE6 and SgcC, the Two-Component Monooxygenase That Catalyzes Hydroxylation of a Carrier Protein-Tethered Substrate during the Biosynthesis of the Enediyne Antitumor Antibiotic C‑1027 in <i>Streptomyces globisporus</i>
C-1027
is a chromoprotein enediyne antitumor antibiotic produced
by <i>Streptomyces globisporus</i>. In the last step of
biosynthesis of the (<i>S</i>)-3-chloro-5-hydroxy-β-tyrosine
moiety of the C-1027 enediyne chromophore, SgcE6 and SgcC compose
a two-component monooxygenase that hydroxylates the C-5 position of
(<i>S</i>)-3-chloro-β-tyrosine. This two-component
monooxygenase is remarkable for two reasons. (i) SgcE6 specifically
reacts with FAD and NADH, and (ii) SgcC is active with only the peptidyl
carrier protein (PCP)-tethered substrate. To address the molecular
details of substrate specificity, we determined the crystal structures
of SgcE6 and SgcC at 1.66 and 2.63 Ã… resolution, respectively.
SgcE6 shares a similar β-barrel fold with the class I HpaC-like
flavin reductases. A flexible loop near the active site of SgcE6 plays
a role in FAD binding, likely by providing sufficient space to accommodate
the AMP moiety of FAD, when compared to that of FMN-utilizing homologues.
SgcC shows structural similarity to a few other known FADH<sub>2</sub>-dependent monooxygenases and sheds light on some biochemically but
not structurally characterized homologues. The crystal structures
reported here provide insights into substrate specificity, and comparison
with homologues provides a catalytic mechanism of the two-component,
FADH<sub>2</sub>-dependent monooxygenase (SgcE6 and SgcC) that catalyzes
the hydroxylation of a PCP-tethered substrate