Muraymycins are antibacterial natural products from Streptomyces spp. that inhibit translocase I (MraY), which is involved in cell wall biosynthesis. Structurally, muraymycins consist of a 5′-C-glycyluridine (GlyU) appended to a 5″-amino-5″-deoxyribose (ADR), forming a disaccharide core that is found in several peptidyl nucleoside inhibitors of MraY. For muraymycins, the GlyU-ADR disaccharide is further modified with an aminopropyl-linked peptide to generate the simplest structures, annotated as the muraymycin D series. Two enzymes encoded in the muraymycin biosynthetic gene cluster, Mur29 and Mur28, were functionally assigned in vitro as a Mg·ATP-dependent nucleotidyltransferase and a Mg·ATP-dependent phosphotransferase, respectively, both modifying the 3″-OH of the disaccharide. Biochemical characterization revealed that both enzymes can utilize several nucleotide donors as cosubstrates and the acceptor substrate muraymycin also behaves as an inhibitor. Single-substrate kinetic analyses revealed that Mur28 preferentially phosphorylates a synthetic GlyU-ADR disaccharide, a hypothetical biosynthetic precursor of muraymycins, while Mur29 preferentially adenylates the D series of muraymycins. The adenylated or phosphorylated products have significantly reduced (170-fold and 51-fold, respectively) MraY inhibitory activities and reduced antibacterial activities, compared with the respective unmodified muraymycins. The results are consistent with Mur29-catalyzed adenylation and Mur28-catalyzed phosphorylation serving as complementary self-resistance mechanisms, with a distinct temporal order during muraymycin biosynthesis.
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This work was supported in part by the National Institutes of Health (grant AI087849), the National Center for Advancing Translational Sciences (grant UL1TR000117), the Fonds der Chemischen Industrie (Germany) (Sachkostenzuschuss to C.D.), and the German federal state of Lower Saxony (Lichtenberg doctoral fellowship [CaSuS program] to A.L.).
Supplemental material for this article may be found at https://doi.org/10.1128/AAC.00193-18.
Cui, Zheng; Wang, Xia-Chang; Liu, Xiaodong; Lemke, Anke; Koppermann, Stefan; Ducho, Christian; Rohr, Jürgen; Thorson, Jon S.; and Van Lanen, Steven G., "Self-Resistance During Muraymycin Biosynthesis: A Complementary Nucleotidyltransferase and Phosphotransferase with Identical Modification Sites and Distinct Temporal Order" (2018). Pharmaceutical Sciences Faculty Publications. 107.