Identification of genes involved in the biosynthesis of the cytotoxic compound glidobactin from a soil bacterium

Abstract

Glidobactins (syn. cepafungins) are a family of structurally related cytotoxic compounds that were isolated from the soil bacterial strain K481-B101 (ATCC 53080; DSM 7029) originally assigned to Polyangium brachysporum and, independently, from an undefined species related to Burkholderia cepacia. Glidobactins are acylated tripeptide derivatives that contain a 12-membered ring structure consisting of the two unique non-proteinogenic amino acids erythro-4-hydroxy-l-lysine and 4(S)-amino-2(E)-pentenoic acid. Here we report the cloning and functional analysis of a gene cluster (glbA-glbH) involved in glidobactin synthesis from K481-B101, which according to its 16S rRNA sequence belongs to the Burkholderiales. The putative encoded proteins include a mixed non-ribosomal peptide/polyketide synthetase whose structure and architecture allowed to build a biosynthetic pathway model explaining the biosynthesis of the unique peptide part of glidobactins. Intriguingly, among the more than 600 bacterial strains whose genome sequence is currently available, homologous gene clusters were found in Burkholderia pseudomallei, the causing agent of melioidosis, and in the insect pathogen Photorhabdus luminescens, strongly suggesting that these organisms are capable to synthesize compounds similar to glidobactins. In addition, a glb gene cluster that was inactivated by transposon-mediated rearrangements was also present in Burkholderia mallei, a very close relative of B. pseudomallei and the causing agent of glanders in horse-like animals.

One-shot NMR analysis of microbial secretions identifies highly potent proteasome inhibitor

“…SylA is produced in vivo by a nonribosomal peptide synthetase, which is constituted by an array of enzymes responsible for attachment of amino acid building blocks and introduction of chemical modifications. SylD, a 460-kDa multidomain enzyme, represents the major part of this assembly line and was chosen for BLAST alignment (17,18). The search yielded hits among various Photorhabdus and Burkholderia species, which can therefore be suggested to produce analogous natural products.…”

Synthetic and structural studies on syringolin A and B reveal critical determinants of selectivity and potency of proteasome inhibition

“…Syrbactins are natural products that share biosynthetic pathways by related gene clusters (16,17). They exhibit an ␣,␤-unsaturated carbonyl system located within a macrocycle that reacts irreversibly with the proteasomal active site Thr1O ␥ by a Michael-type 1,4-addition.…”

Syringolin A: Action on Plants, Regulation of Biosynthesis and Phylogenetic Occurrence of Structurally Related Compounds

“…This fragment was used to isolate the complete gene cluster from DSM 7029 ( Figure 2B). Insertion mutants confirmed that this cluster encoded the glidobactin A synthetase (Schellenberg et al, 2007). This analysis suggests that B. pseudomallei and P. luminescens are able to produce glidobactin-like compounds.…”