Filamentation and inhibition of prokaryotic CTP synthase with ligands

Glutamate kinase (GK) is the first committed enzyme in the proline biosynthesis pathway. Belonging to amino acid kinase (AAK) superfamily, most prokaryotic GKs have an additional PseudoUridine synthase and Archaeosine transglycosylase (PUA) domain at the C-terminus, while the function of the PUA domain in GK is poorly understood. Here, we find that Escherichia coli GK (EcGK) assembles into filaments and bundles in the state of apo and proline binding. Using cryogenic electron microscopy, we determine the high-resolution structures of EcGK filaments and bundles. The PUA domain is necessary for EcGK filaments and bundles, and the main interfaces have been clearly defined. The feedback inhibitor proline binds at the same pocket as substrate glutamate, inducing conformational changes on nearby regulatory loop which facilitate proline binding. The PUA domain stabilizes the regulatory loop and contributes to proline feedback inhibition. This study reports the special filament-based assembly of EcGK at apo and proline binding state. The first proline binding structure in the GK family illustrates the feedback inhibition mechanism. Intriguingly, the PUA domain is involved in both filamentation and feedback inhibition of EcGK, revealing the versatility of this ancient domain.

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Cytoophidium complexes resonate with cell fates

Li,

Liu

2024

Preprint

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Metabolism is a fundamental characteristic of life. In 2010, we discovered that the metabolic enzyme CTP synthase (CTPS) can assemble a snake like structure inside cells, which we call the cytoophidium. Including CTPS, an increasing number of metabolic enzymes have been found to form cytoophidia in cells. However, the distribution and relationship among cytoophidia formed by different metabolic enzymes remain elusive. Here we investigate five metabolic enzymes that can form cytoophidia, namely Asn1, Bna5, CTPS (ie. Ura7), Glt1, and Prs5 in Saccharomyces cerevisiae. We find that multiple cytoophidia can be assembled into cytoophidium complexes by docking one after another. Glt1 cytoophidia tend to assemble in non-quiescent cells, while CTPS cytoophidia are more abundant in quiescent cells and form complexes with Prs5 and Asn1 cytoophidia. Blocking CTPS cytoophidium assembly can lead to a non-quiescent phenotype and increase the assembly of Glt1 cytoophidia, Bna5 cytoophidia, and cytoophidium complexes. Blocking CTPS cytoophidium assembly also inhibits the NAD biosynthesis pathway, which includes Bna5 and Sir2. Consistent with this result, the non-quiescent phenotype caused by blocking CTPS cytoophidium assembly can be rescued by blocking Glt1 cytoophidium assembly, supplementing nicotinic acid, or overexpressing Sir2. Our results indicate that the assembly of cytoophidium complexes with different compositions resonates with distinct cell fates.

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Filamentation and inhibition of prokaryotic CTP synthase with ligands

Cited by 4 publications

References 41 publications

Structural Basis of Bifunctional CTP/dCTP Synthase

Structural Basis of Bifunctional CTP/dCTP Synthase

Filamentation and proline inhibition of glutamate kinase

Cytoophidium complexes resonate with cell fates

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