Discovery of 23 Natural Tubulysins from Angiococcus disciformis An d48 and Cystobacter SBCb004

Abstract

The tubulysins are a family of complex peptides with promising cytotoxic activity against multi-drug-resistant tumors. To date, ten tubulysins have been described from the myxobacterial strains Angiococcus disciformis An d48 and Archangium gephyra Ar 315. We report here a third producing strain, Cystobacter sp. SBCb004. Comparison of the tubulysin biosynthetic gene clusters in SBCb004 and An d48 reveals a conserved architecture, allowing the assignment of cluster boundaries. A SBCb004 strain containing a mutant in the putative cyclodeaminase gene tubZ accumulates pretubulysin A, the proposed first enzyme-free intermediate in the pathway, whose structure we confirm by NMR. We further show, using a combination of feeding studies and structure elucidation by NMR and high-resolution tandem mass spectrometry, that SBCb004 and An d48 together biosynthesize 22 additional tubulysin derivatives. These data reveal the inherently diversity-oriented nature of the tubulysin biosynthetic pathway.

Biosynthetic Modularity Rules in the Bisintercalator Family of Antitumor Compounds

“…Homologues to this enzyme have been also described in FK-506 (FkbL, Streptomyces sp. kMA6548 ), virginiamycin S (VisC, Streptomyces virginiae ) and tubulysin (TubZ, Angiococcus disciformis ) pathways [56,57,58]. Sandramycin and quinaldopeptin gene clusters, must therefore contain rapL homologues, as these bisintercalators contain l -pipecolic acid.…”

Syntheses and Evaluation of Simplified Pretubulysin Analogues

“…[7] Very recently, further derivatives were discovered in A. disciformis An d48 and Cystobacter SBCb004 by the Müller group. [8] Common to all members of the tubulysin family is their linear structure, beginning with an N-terminal Nmethylated d-pipecolinic acid (d-Mep), followed by the only proteinogenic amino acid l-Ile. The next building block is called tubuvaline (Tuv), an unusual thiazole amino acid, bound through an exotic acylated N,O-acetal structure.…”

Paradigm Shifts in Fungal Secondary Metabolite Research: Unusual Fatty Acids Incorporated into Fungal Peptides

“…Thiomarinols D, E, F, and G exhibited antimicrobial activities against Gram-positive and Gram-negative bacteria. They were especially active against Gram-positive bacteria including methicillinresistant Staphylococcus aureus (Ullrich et al, 2009;Khalil et al, 2006;Chai et al, 2010).…”