Identification of Cyclic Depsipeptides and Their Dedicated Synthetase from Hapsidospora irregularis

Abstract

Seven cyclic depsipeptides were isolated from Hapsidospora irregularis and structurally characterized as the calcium channel blocker leualacin and six new analogues based on the NMR and HR-ESI-MS data. These new compounds were named leualacins B-G. The absolute configurations of the amino acids and 2-hydroxyisocaproic acids were determined by recording the optical rotation values. Biological studies showed that calcium influx elicited by leualacin F in primary human lobar bronchial epithelial cells involves the TRPA1 channel. Through genome sequencing and targeted gene disruption, a non-iterative nonribosomal peptide synthetase was found to be involved in the biosynthesis of leualacin. A comparison of the structures of leualacin and its analogues indicated that the A2 and A4 domains of the leualacin synthetase are substrate specific, while A1, A3 and A5 can accept alternative precursors to yield new molecules.

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“…6, 7). The pattern was consistent with a previous classification of NRPS A-domains (Bushley et al 2013; Bushley and Turgeon 2010), except that the inclusion of fifth A-domain a leualacin NRPS (Zhang et al 2017a) was aligned with the A-domains of group 1. The other four A-domains from the leualacin NRPS were close orthologs of the destruxin NRPS (Fig.…”

“…Similarity searches with the predicted AA sequence of the A-domain from the sixth module of the CsC NRPS indicated a high identity to NRPS modules from seven other fungal peptides (CsA, aureobasidin A, bassianolide, enniatin A–C, beauvericin, leualacin, and destruxin A–F) (Bushley et al 2013; Zhang et al 2017a). A comparison of the predicted and actual AAs from each peptide and the corresponding A-domain binding pocket sequence (Stachelhaus codes) was compiled (Table 2).…”

Structural Diversity and Biological Activities of Cyclic Depsipeptides from Fungi

“…Afterwards, six other anlogues, leualacins B–G ( 74 – 79 ) were obtained from this fungal species. Leualacin F ( 78 ) elicited the calcium influx in primary human lobar bronchial epithelial cells involving the TRPA1 channel [ 68 ].…”

Biosynthesis of depsipeptides, or Depsi: The peptides with varied generations

“…Ester bond insertion by direct selection and incorporation of α-hydroxy acid occurs twice leualacin Figure 4): Leualacin is a cyclic depsipeptide which has two α-hydroxyacyl residues 140 and acts as a potent calcium channel blocker. 141 The fivemodule NRPS responsible for its biosynthesis was identified by genome sequencing and gene disruption.…”

“…141 The fivemodule NRPS responsible for its biosynthesis was identified by genome sequencing and gene disruption. 140 Based on the collinearity rule, it is assumed that the A domains in Modules 2 and 4 select α-hydroxy-isocaproic acid (leucic acid), and the C domains of these modules almost certainly perform ester bond formation.…”