4hx6
Streptomyces globisporus C-1027 NADH:FAD oxidoreductase SgcE6
Structural highlights
FunctionSGCE6_STRGL Reductase component of a two-component system involved in the biosynthesis of the enediyne antitumor antibiotic C-1027 (PubMed:18426211, PubMed:19817865). SgcE6 provides the FADH(2) required by both the halogenase SgcC3 and the monooxygenase SgcC through free diffusion (PubMed:18426211, PubMed:19817865). Accepts only NADH and FAD as substrates (PubMed:19817865).[1] [2] Publication Abstract from PubMedC-1027 is a chromoprotein enediyne antitumor antibiotic produced by Streptomyces globisporus. In the last step of biosynthesis of the (S)-3-chloro-5-hydroxy-beta-tyrosine moiety of the C-1027 enediyne chromophore, SgcE6 and SgcC compose a two-component monooxygenase that hydroxylates the C-5 position of (S)-3-chloro-beta-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 A resolution, respectively. SgcE6 shares a similar beta-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 FADH2-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, FADH2-dependent monooxygenase (SgcE6 and SgcC) that catalyzes the hydroxylation of a PCP-tethered substrate. 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 Streptomyces globisporus.,Chang CY, Lohman JR, Cao H, Tan K, Rudolf JD, Ma M, Xu W, Bingman CA, Yennamalli RM, Bigelow L, Babnigg G, Yan X, Joachimiak A, Phillips GN Jr, Shen B Biochemistry. 2016 Sep 13;55(36):5142-54. doi: 10.1021/acs.biochem.6b00713. Epub , 2016 Sep 1. PMID:27560143[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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