title: Biosynthesis of streptolidine involved two unexpected intermediates produced by a dihydroxylase and a cyclase through unusual mechanisms.
abstract: Streptothricin-F (STT-F), one of the early-discovered antibiotics, consists of three components, a β-lysine homopolymer, an aminosugar D-gulosamine, and an unusual bicyclic streptolidine. The biosynthesis of streptolidine is a long-lasting but unresolved puzzle. Herein, a combination of genetic/biochemical/structural approaches was used to unravel this problem. The STT gene cluster was first sequenced from a Streptomyces variant BCRC 12163, wherein two gene products OrfP and OrfR were characterized in vitro to be a dihydroxylase and a cyclase, respectively. Thirteen high-resolution crystal structures for both enzymes in different reaction intermediate states were snapshotted to help elucidate their catalytic mechanisms. OrfP catalyzes an Fe(II) -dependent double hydroxylation reaction converting L-Arg into (3R,4R)-(OH)2 -L-Arg via (3S)-OH-L-Arg, while OrfR catalyzes an unusual PLP-dependent elimination/addition reaction cyclizing (3R,4R)-(OH)2 -L-Arg to the six-membered (4R)-OH-capreomycidine. The biosynthetic mystery finally comes to light as the latter product was incorporation into STT-F by a feeding experiment.
authors: Genomics Research Center, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 115 (Taiwan).
authors: Chin-Yuan
authors: CY
authors: Chang
authors: Syue-Yi
authors: SY
authors: Lyu
authors: Yu-Chen
authors: YC
authors: Liu
authors: Ning-Shian
authors: NS
authors: Hsu
authors: Chih-Chung
authors: CC
authors: Wu
authors: Cheng-Fong
authors: CF
authors: Tang
authors: Kuan-Hung
authors: KH
authors: Lin
authors: Jin-Yuan
authors: JY
authors: Ho
authors: Chang-Jer
authors: CJ
authors: Wu
authors: Ming-Daw
authors: MD
authors: Tsai
authors: Tsung-Lin
authors: TL
authors: Li
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D006900:Hydroxylation; D006899:Mixed Function Oxygenases / Q000737:chemistry; D013309:Streptothricins / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000596:Amino Acids; C003349:streptolidine; C009156:streptothricin F; D013309:Streptothricins; D006899:Mixed Function Oxygenases
keywords: biosynthesis; enzymes; isotopic labeling; protein structures; reaction mechanisms