Category Archives: Amany Ragab

Biogenesis of the Unique 4 ‘,5 ‘-Dehydronucleoside of the Uridyl Peptide Antibiotic Pacidamycin

Amany E. Ragab ; Sabine Grüschow ; Daniel R. Tromans ; Rebecca J. M. Goss

JACS 2011, 133 (39) 15288-15291

The pacidamycins belong to a class of antimicrobial nucleoside antibiotics that act by inhibiting the clinically unexploited target translocase I, a key enzyme in peptidoglycan assembly. As with other nucleoside antibiotics, the pacidamycin 4′,5′-dehydronucleoside portion is an essential pharmacophore. Here we show that the biosynthesis of the pacidamycin nucleoside in Streptomyces coeruleorubidus proceeds through three steps from uridine. The transformations involve oxidation of the 5′-alcohol by Pac11, transamination of the resulting aldehyde by Pac5, and dehydration by the Cupin-domain protein Pac13.

Pacidamycin Biosynthesis : Identification and Heterologous Expression of the First Uridyl Peptide Antibiotic Gene Cluster

Emma J. Rackham ; Sabine Grüschow ; Amany E. Ragab ; Shilo Dickens ; Rebecca J. M. Goss

ChemBioChem 2010, 11 (12) 1700-1709

The pacidamycins are antimicrobial nucleoside antibiotics produced by Streptomyces coeruleorubidus that inhibit translocase I, an essential bacterial enzyme yet to be clinically targeted. The novel pacidamycin scaffold is composed of a pseudopeptide backbone linked by a unique exocyclic enamide to an atypical 3′-deoxyuridine nucleoside. In addition, the peptidyl chain undergoes a double inversion caused by the incorporation of a diamino acid residue and a rare internal ureido moiety. The pacidamycin gene cluster was identified and sequenced, thereby providing the first example of a biosynthetic cluster for a member of the uridyl peptide family of antibiotics. Analysis of the 22 ORFs provided an insight into the biosynthesis of the unique structural features of the pacidamycins. Heterologous expression in Streptomyces lividans resulted in the production of pacidamycin D and the newly identified pacidamycin S, thus confirming the identity of the pacidamycin biosynthetic gene cluster. Identification of this cluster will enable the generation of new uridyl peptide antibiotics through combinatorial biosynthesis. The concise cluster will provide a useful model system through which to gain a fundamental understanding of the way in which nonribosomal peptide synthetases interact.

New pacidamycins biosynthetically: probing N- and C-terminal substrate specificity

Amany E. Ragab ; Sabine Grüschow ; Emma J. Rackham ; Rebecca J. M. Goss

Org Biomol Chem 2010, 8 3128-3129

Feeding phenylalanine analogues to Streptomyces coeruleorubidus reveals the remarkable steric and electronic flexibility of this biosynthetic pathway and leads to the generation of a series of new halopacidamycins.

Graphical abstract: New pacidamycins biosynthetically: probing N- and C-terminal substrate specificity