Cyanophycin and its biosynthesis: not hot but very cool

Sharon, Itai; Hilvert, Donald; Schmeing, T.M.

doi:10.1039/d2np00092j

Cited by 3 publications

(1 citation statement)

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“…Cyanophycin is a natural polymer produced by a wide range of bacteria (Sharon et al, 2021; Sharon, Hilvert, & Schmeing, 2023). Discovered in cyanobacteria over a century ago (Borzi, 1886‐1887), it is composed of a poly‐L‐aspartate backbone with arginine residues covalently attached to the aspartate sidechains (Allen & Weathers, 1980) (Figure 1a).…”

Section: Introductionmentioning

confidence: 99%

Structure and function of a hexameric cyanophycin synthetase 2

et al. 2023

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Cyanophycin is a natural polymer composed of a poly‐aspartate backbone with arginine attached to each of the aspartate sidechains. Produced by a wide range of bacteria, which mainly use it as a store of fixed nitrogen, it has many promising industrial applications. Cyanophycin can be synthesized from the amino acids Asp and Arg by the widespread cyanophycin synthetase 1 (CphA1), or from the dipeptide β‐Asp‐Arg by the cyanobacterial enzyme cyanophycin synthetase 2 (CphA2). CphA2 enzymes display a range of oligomeric states, from dimers to dodecamers. Recently, the crystal structure of a CphA2 dimer was solved but could not be obtained in complex with substrate. Here, we report cryo‐EM structures of the hexameric CphA2 from Stanieria sp. at ~2.8 Å resolution, both with and without ATP analog and cyanophycin. The structures show a two‐fold symmetrical, trimer‐of‐dimers hexameric architecture, and substrate‐binding interactions that are similar to those of CphA1. Mutagenesis experiments demonstrate the importance of several conserved substrate‐binding residues. We also find that a Q416A/R528G double mutation prevents hexamer formation and use this double mutant to show that hexamerization augments the rate of cyanophycin synthesis. Together, these results increase our mechanistic understanding of how an interesting green polymer is biosynthesized.

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Section: Introductionmentioning

confidence: 99%

Structure and function of a hexameric cyanophycin synthetase 2

et al. 2023

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Structural and functional insights into δ-poly-L-ornithine polymer biosynthesis from Acinetobacter baumannii

Patel,

Gulick

2023

Commun Biol

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Cationic homo-polyamino acid (CHPA) peptides containing isopeptide bonds of diamino acids have been identified from Actinomycetes strains. However, none has been reported from other bacteria. Here, we report a δ-poly-L-ornithine synthetase from Acinetobacter baumannii, which we name PosA. Surprisingly, structural analysis of the adenylation domain and biochemical assay shows L-ornithine as the substrate for PosA. The product from the enzymatic reaction was purified and identified as poly-L-ornithine composed of 7-12 amino acid units. Chemical labeling of the polymer confirmed the isopeptide linkage of δ-poly-L-ornithine. We examine the biological activity of chemically synthesized 12-mer δ-poly-L-ornithine, illustrating that the polymer may act as an anti-fungal agent. Structures of the isolated adenylation domain from PosA are presented with several diamino acids and biochemical assays identify important substrate binding residues. Structurally-guided genome-mining led to the identification of homologs with different substrate binding residues that could activate additional substrates. A homolog from Bdellovibrionales sp. shows modest activity with L-arginine but not with any diamino acids observed to be substrates for previously examined CHPA synthetases. Our study indicates the possibility that additional CHPAs may be produced by various microbes, supporting the further exploration of uncharacterized natural products.

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Structure and function of a hexameric cyanophycin synthetase 2

Markus¹,

Sharon²,

Munro³

et al. 2023

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Cyanophycin is a natural polymer composed of a poly-aspartate backbone with arginine attached to each of the aspartate sidechains. Produced by a wide range of bacteria, which mainly use it as a store of fixed nitrogen, it has many promising industrial applications. Cyanophycin can be synthesized from the amino acids Asp and Arg by the widespread cyanophycin synthetase 1 (CphA1), or from the dipeptide β-Asp-Arg by the cyanobacterial enzyme cyanophycin synthetase 2 (CphA2). CphA2 enzymes display a range of oligomeric states, from dimers to dodecamers. Recently, the crystal structure of a CphA2 dimer was solved but could not be obtained in complex with substrate. Here, we report cryo-EM structures of the hexameric CphA2 from Stanieria sp. at ~2.8 A resolution, both with and without ATP and cyanophycin. The structures show a trimer-of-dimers hexameric architecture, and substrate-binding interactions that are similar to those of CphA1. Mutagenesis experiments demonstrate the importance of several conserved substrate-binding residues. We also find that a Q416A/R528G double mutation prevents hexamer formation and use this double mutant to show that hexamerization augments the rate of cyanophycin synthesis. Together, these results increase our mechanistic understanding of how an interesting green polymer is biosynthesized.

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Cyanophycin and its biosynthesis: not hot but very cool

Abstract: Cyanophycin is a widespread natural biopolymer with promising green chemistry applications that is made by an elegant, multifunctional biosynthetic machine.

Cited by 3 publications

References 157 publications

Structure and function of a hexameric cyanophycin synthetase 2

Structure and function of a hexameric cyanophycin synthetase 2

Structural and functional insights into δ-poly-L-ornithine polymer biosynthesis from Acinetobacter baumannii

Structure and function of a hexameric cyanophycin synthetase 2

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