Category Archives: Sabine Grüschow

Filipins: the first antifungal “weed killers” identified from bacteria isolated from the trap-ant

Allomerus ants ensure that they have sufficient nitrogen in their diet by trapping and consuming other insects. In order to construct their traps, like the more extensively studied leaf cutter ants, they employ fungal farming. Pest management within these fungal cultures has been speculated to be due to the ants’ usage of actinomycetes capable of producing antifungal compounds, analogous to the leafcutter ant mutualism. Here we report the first identification of a series of antifungal compounds, the filipins, and their associated biosynthetic genes isolated from a bacterium associated with this system.

Gao H, Grüschow S, Barke J, Seipke RF, Hill LM, Orivel K, Yu DW, Hutchings M, Goss RJM

RSC Adv. 2014, 4, 57267

Scope and potential of halogenases in biosynthetic applications

Smith DRM; Grüschow S; Goss RJM

Curr Opin Chem Biol 2012, 17 (2) 276-283

A large and diverse series of halogenated natural products exist. In many of these compounds the halogen is important to biological activity and bioavailability. We now recognise that nature has developed many different halogenation strategies for which well-known enzyme classes such as haem oxidases or flavin-dependent oxidases have been adapted. Enzymes capable of halogenating all kinds of different chemical groups from electron-rich to electron-poor, from aromatic to aliphatic have been characterised. Given that synthetic halogenation reactions are not trivial transformations and that halogenated molecules possess pharmaceutical usefulness, it will be worth investing into further research of halogenating enzymes.

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.

Diversity in natural product families is governed by more than enzyme promiscuity alone : establishing control of the pacidamycin portfolio

Sabine Grüschow ; Emma J. Rackham ; Rebecca J. M. Goss

Chem Sci 2011, 2 2182-2186

As with many other antibiotics, pacidamycins are produced as a suite of related compounds. Unlike most other secondary metabolites, however, this diversity is not solely the result of the substrate promiscuity of the biosynthetic enzymes but also arises from a gene duplication event (Pac21, Pac21h) and control of the precursor pool (PhhA). We are demonstrating the ability to harness these three levels of control in order to direct the selective production of specific members of this family of metabolites in a “dial-a-molecule” fashion. Furthermore, PhhA is shown to be a phenylalanine 3-hydroxylase, the first of the iron- and tetrahydropterin-dependentaromatic amino acid hydroxylases to be characterised with this regioselectivity.

Graphical abstract: Diversity in natural product families is governed by more than enzyme promiscuity alone: establishing control of the pacidamycin portfolio

Gene Expression Enabling Synthetic Diversification of Natural Products : Chemogenetic Generation of Pacidamycin Analogs

Abhijeet Deb Roy ; Sabine Grueschow ; Nickiwe Cairns ; Rebecca J. M. Goss

JACS 2010, 132 (35) 12243-12245

Introduction of prnA, the halogenase gene from pyrrolnitrin biosynthesis, into Streptomyces coeruleorubidus resulted in efficient in situ chlorination of the uridyl peptide antibotic pacidamycin. The installed chlorine provided a selectably functionalizable handle enabling synthetic modification of the natural product using mild cross-coupling conditions in crude aqueous extracts of the culture broth.

A mixed community of actinomycetes produce multiple antibiotics for the fungus farming ant Acromyrmex octospinosus

Joerg Barke ; Ryan F. Seipke ; Sabine Grueschow ; Darren Heavens ; Nizar Drou ; Mervyn J. Bibb ; Rebecca J. M. Goss ; Douglas W. Yu ; Matthew I. Hutchings

BMC Biology 2010, 8 109

ttine ants live in an intensely studied tripartite mutualism with the fungus Leucoagaricus gongylophorus, which provides food to the ants, and with antibiotic-producing actinomycete bacteria. One hypothesis suggests that bacteria from the genus Pseudonocardia are the sole, co-evolved mutualists of attine ants and are transmitted vertically by the queens. A recent study identified a Pseudonocardia-produced antifungal, named dentigerumycin, associated with the lower attine Apterostigma dentigerum consistent with the idea that co-evolved Pseudonocardia make novel antibiotics. An alternative possibility is that attine ants sample actinomycete bacteria from the soil, selecting and maintaining those species that make useful antibiotics. Consistent with this idea, a Streptomyces species associated with the higher attine Acromyrmex octospinosus was recently shown to produce the well-known antifungal candicidin. Candicidin production is widespread in environmental isolates of Streptomyces, so this could either be an environmental contaminant or evidence of recruitment of useful actinomycetes from the environment. It should be noted that the two possibilities for actinomycete acquisition are not necessarily mutually exclusive.

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

New Pacidamycin Antibiotics Through Precursor-Directed Biosynthesis

Sabine Gruschow ; Emma J. Rackham ; Benjamin Elkins ; Philip L. A. Newilll ; Lionel M. Hill ; Rebecca J. M. Goss

ChemBioChem 2009, 10 (2) 355-360

Pacidamycins, mureidomycins and napsamycins are structurally related uridyl peptide antibiotics that inhibit translocase I, an as yet clinically unexploited target. This potentially important bioactivity coupled to the biosynthetically intriguing structure of pacidamycin make this natural product a fascinating subject for study. A precursor-directed biosynthesis approach was employed in order to access new pacidamycin derivatives. Strikingly, the biosynthetic machinery exhibited highly relaxed substrate specificity with the majority of the tryptophan analogues that were administered; this resulted in the production of new pacidamycin derivatives. Remarkably, 2-methyl-, 7-methyl-, 7-chloro- and 7-bromotryptophans produced their corresponding pacidamycin analogues in larger amounts than the natural pacidamycin. Low levels or no incorporation was observed for tryptophans substituted at positions 4, 5 and 6. The ability to generate bromo- and chloropacidamycins opens up the possibility of further functionalising these compounds through chemical cross-coupling in order to access a much larger family of derivatives.