Fig. 4: Proposed biosynthetic models for SidC-catalysed formation of ferricrocin and ferrichrome. | Nature Communications

Fig. 4: Proposed biosynthetic models for SidC-catalysed formation of ferricrocin and ferrichrome.

From: Elucidating the molecular programming of a nonlinear non-ribosomal peptide synthetase responsible for fungal siderophore biosynthesis

Fig. 4: Proposed biosynthetic models for SidC-catalysed formation of ferricrocin and ferrichrome.The alternative text for this image may have been generated using AI.

a Ferricrocin (2) biosynthesis commences with condensation between l-Ser and Gly, which is catalysed by the SidC C2 domain forming an (l-Ser)-Gly dipeptide (n = 2) tethered to the SidC T2 domain. Non-canonical ligation of a Gly unit onto the amine of l-Ser produces a Gly-(l-Ser)-Gly tripeptide (n = 3), which can undergo condensation with l-AHO catalysed by the chain-length selective SidC C3 domain. The SidC A3 domain loads l-AHO onto SidC T4 and T5 domains allowing a succession of condensation events to generate a Gly-(l-Ser)-Gly-(l-AHO)3 hexapeptide intermediate bound to the SidC T5 domain. Chain release is catalysed by the C-terminal CT domain to yield the biosynthetic product 9. b Ferrichrome (3) biosynthesis can occur in the absence of l-Ser, where canonical loading of Gly onto the T2 domain is followed by two successive rounds of non-canonical Gly ligation to yield a Gly3 species (n = 3) tethered to the T2 domain. The remaining steps are identical to the biosynthesis of 2, to yield the biosynthetic product 3.

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