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Download fileCharacterization of a C3 Deoxygenation Pathway Reveals a Key Branch Point in Aminoglycoside Biosynthesis
journal contribution
posted on 2016-04-27, 00:00 authored by Meinan Lv, Xinjian Ji, Junfeng Zhao, Yongzhen Li, Chen Zhang, Li Su, Wei Ding, Zixin Deng, Yi Yu, Qi ZhangApramycin is a clinically
interesting aminoglycoside antibiotic
(AGA) containing a highly unique bicyclic octose moiety, and this
octose is deoxygenated at the C3 position. Although the biosynthetic
pathways for most 2-deoxystreptamine-containing AGAs have been well
characterized, the pathway for apramycin biosynthesis, including the
C3 deoxygenation process, has long remained unknown. Here we report
detailed investigation of apramycin biosynthesis by a series of genetic,
biochemical and bioinformatical studies. We show that AprD4 is a novel
radical S-adenosyl-l-methionine (SAM) enzyme,
which uses a noncanonical CX3CX3C motif for
binding of a [4Fe-4S] cluster and catalyzes the dehydration of paromamine,
a pseudodisaccharide intermediate in apramycin biosynthesis. We also
show that AprD3 is an NADPH-dependent reductase that catalyzes the
reduction of the dehydrated product from AprD4-catalyzed reaction
to generate lividamine, a C3′ deoxygenated product of paromamine.
AprD4 and AprD3 do not form a tight catalytic complex, as shown by
protein complex immunoprecipitation and other assays. The AprD4/AprD3
enzyme system acts on different pseudodisaccharide substrates but
does not catalyze the deoxygenation of oxyapramycin, an apramycin
analogue containing a C3 hydroxyl group on the octose moiety, suggesting
that oxyapramycin and apramycin are partitioned into two parallel
pathways at an early biosynthetic stage. Functional dissection of
the C6 dehydrogenase AprQ shows the crosstalk between different AGA
biosynthetic gene clusters from the apramycin producer Streptomyces
tenebrarius, and reveals the remarkable catalytic versatility
of AprQ. Our study highlights the intriguing chemistry in apramycin
biosynthesis and nature’s ingenuity in combinatorial biosynthesis
of natural products.
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AGA biosynthetic gene clustersSAMC 3 positionC 3 hydroxyl groupC 3 deoxygenation processcatalyzeC 6 dehydrogenase AprQnoncanonical CX 3 CX 3 C motifapramycin producer Streptomyces tenebrariusbicyclic octose moietyapramycin biosynthesisAminoglycoside Biosynthesis ApramycinKey Branch PointpathwayC 3 Deoxygenation PathwayAprD 3AprD 4