Engineering the Biosynthesis of the Polyketide-Nonribosomal Peptide Collismycin A for Generation of Analogs with Neuroprotective Activity

Abstract

Collismycin A is a member of the 2,2'-bipyridyl family of natural products that shows cytotoxic activity. Structurally, it belongs to the hybrid polyketides-nonribosomal peptides. After the isolation and characterization of the collismycin A gene cluster, we have used the combination of two different approaches (insertional inactivation and biocatalysis) to increase structural diversity in this natural product class. Twelve collismycin analogs were generated with modifications in the second pyridine ring of collismycin A, thus potentially maintaining biologic activity. None of these analogs showed better cytotoxic activity than the parental collismycin. However, some analogs showed neuroprotective activity and one of them (collismycin H) showed better values for neuroprotection against oxidative stress in a zebrafish model than those of collismycin A. Interestingly, this analog also showed very poor cytotoxic activity, a feature very desirable for a neuroprotectant compound.

Biochemical and Structural Insights into the Aminotransferase CrmG in Caerulomycin Biosynthesis

“…Similarly, hydroxymethyl-containing collismycin analogues were accumulated in the ΔclmAT (encoding a CrmG-like aminotransferase) mutant and were shown as shunt products in collismycin biosynthesis via feeding experiments. 17 Thus, we reasoned that the natural substrate of CrmG should contain an aldehyde group as previously proposed ( Figure 1). 15,20 Therefore, the compounds CRM M 4 and CRM E 9 were prepared from CRM H 6 and 1 ( Figure 3A), respectively, by chemical deoximation.…”

Heteroatom–Heteroatom Bond Formation in Natural Product Biosynthesis

“…146,152,153 A flavin-dependent monooxygenase ClmM has been implicated in late-stage oxime formation because a clmM deletion mutant accumulated the corresponding N- acetylamine shunt product. 154 In vitro characterization of ClmM has not yet been reported, but based on the similarities of the collismycin and caerulomycin structures and biosynthetic gene custers, ClmM is expected to display reactivity similar to CrmH.…”

Unique post-translational oxime formation in the biosynthesis of the azolemycin complex of novel ribosomal peptides from Streptomyces sp. FXJ1.264

“…32,33 Finally, in collismycin biosynthesis, the putative flavin-dependent monooxygenase ClmM, which shares 46% sequence identity with AzmF, is implicated in the oxidation of a primary amine to the corresponding oxime. 34 …”