Shared PKS Module in Biosynthesis of Synergistic Laxaphycins

Abstract

Cyanobacteria produce a wide range of lipopeptides that exhibit potent membranedisrupting activities. Laxaphycins consist of two families of structurally distinct macrocyclic lipopeptides that act in a synergistic manner to produce antifungal and antiproliferative activities. Laxaphycins are produced by range of cyanobacteria but their biosynthetic origins remain unclear. Here, we identified the biosynthetic pathways responsible for the biosynthesis of the laxaphycins produced by Scytonema hofmannii PCC 7110. We show that these laxaphycins, called scytocyclamides, are produced by this cyanobacterium and are encoded in a single biosynthetic gene cluster with shared polyketide synthase enzymes initiating two distinct non-ribosomal peptide synthetase pathways. The unusual mechanism of shared enzymes synthesizing two distinct types of products may aid future research in identifying and expressing natural product biosynthetic pathways and in expanding the known biosynthetic logic of this important family of natural products.

The structure and biosynthesis of heinamides A1–A3 and B1–B5, antifungal members of the laxaphycin lipopeptide family

“…Twenty-four laxaphycin structures have been described in the literature with antifungal, antiproliferative, and antibacterial activities [7][8][9][10][11][12][27][28][29][30][31][32][33][34][35][36][37][38] (Table S1 †). Here we report eight new laxaphycin variants, which we call heinamides.…”

“…UHCC 0702 and S. hofmannii PCC 7110 genomes. The condensation domain of LxaC1 3 was analyzed with Natural Product Domain Seeker (NaPDoS) 24 and compared with other known Dhb-related condensation domains LxaC1 3 , HasO 2 , NdaA 1 , and PuwF 2 , which are involved in the biosynthesis of scytocyclamides, 10 hassalladins, 25 nodularins, 20 and puwainaphycins, 26 respectively.…”

“…The 11-residue heinamides follow the amino acid sequence Aoa 1 -Ser 2 -Dhb 3 -((2S,4R)-4-OHPro/Pro) 4 -Ser 5 -Tyr 6 -Leu 7 -Ile 8 -Phe 9 -((2S,4R)-4-OHPro/Pro) 10 -Gly 11 ; the difference between variants was the hydroxylation of Pro 4,10 . The 12-residue heinamides have the amino acid sequence (Aoa/5-OH-Aoa) 1 -Ile 2 -OHLeu 3 -(O-carbamoyl-Hse) 4 -Leu 5 -Gln 6 -(N-Me-Ile) 7 -OHHse 8 -Val 9 -(OHMePro/ Pro/4-MePro) 10 -Tyr 11 -Thr 12 , where the differences between variants is in the hydroxylation of the octanoic acid 1 and hydroxylation and methylation of the Pro 10 . The stereochemistry of the compounds is derived from stereospecific amino acid analysis (Table S11 †) and NMR.…”

“…7,8 Laxaphycins include characteristic non-proteinogenic amino acids, including 3-hydroxy-Dleucine (OHLeu), 3-hydroxy-D-asparagine (OHAsn), dehydrobu-tyrine (Dhb), and (2S,4R)-4-hydroxyproline ((2S,4R)-4-OHPro). 9,10 Altogether 17 variants of 11-residue laxaphycins and 23 variants of 12-residue laxaphycins have been described from a broad range of cyanobacteria (Table S1 †). Although 11and 12-residue types are both found in most producer strains, there are reports of strains for which only one type of the compound is reported.…”

“…11,12 In an earlier study, we described the biosynthetic pathway of scytocyclamides, which belong to the laxaphycin peptide family. 10 This pathway includes a shared initiating fatty-acyl AMP ligase (FAAL) and a polyketide synthase (PKS) module that branches with two non-ribosomal peptide synthetase (NRPS) pathways to produce the two distinct 11-and 12-residue compounds. 10 Scytocyclamides are produced by Scytonema hofmannii PCC 7110.…”