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Substrate-binding loop interactions with pseudouridine trigger conformational changes that promote catalytic efficiency of pseudouridine kinase PUKI.

ABSTRACT: Pseudouridine, one major RNA modification, is catabolized into uracil and ribose-5'-phosphate by two sequential enzymatic reactions. In the first step, pseudouridine kinase (PUKI) phosphorylates pseudouridine to pseudouridine 5'-monophosphate. High-fidelity catalysis of pseudouridine by PUKI prevents possible disturbance of in vivo pyrimidine homeostasis. However, the molecular basis of how PUKI selectively phosphorylates pseudouridine over uridine with >100-fold greater efficiency despite minor differences in their K_m values has not been elucidated. To investigate this selectivity, in this study we determined the structures of PUKI from Escherichia coli strain B (EcPUKI) in various ligation states. The structure of EcPUKI was determined to be similar to PUKI from Arabidopsis thaliana, including an α/β core domain and β-stranded small domain, with dimerization occurring via the β-stranded small domain. In a binary complex, we show that Ser30 in the substrate-binding loop of the small domain mediates interactions with the hallmark N1 atom of pseudouridine nucleobase, causing conformational changes in its quaternary structure. Kinetic and fluorescence spectroscopic analyses also showed that the Ser30-mediated interaction is a prerequisite for conformational changes and subsequent catalysis by EcPUKI. Furthermore, S30A mutation or EcPUKI complexed with other nucleosides homologous to pseudouridine but lacking the pseudouridine-specific N1 atom did not induce such conformational changes, demonstrating the catalytic significance of the proposed Ser30-mediated interaction. These analyses provide structural and functional evidence for a pseudouridine-dependent conformational change of EcPUKI and its functional linkage to catalysis.

SUBMITTER: Kim SH

PROVIDER: S-EPMC9061257 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Substrate-binding loop interactions with pseudouridine trigger conformational changes that promote catalytic efficiency of pseudouridine kinase PUKI.

Kim Sang-Hoon SH Kim Minjeong M Park Daechan D Byun Sujeong S Rhee Sangkee S

The Journal of biological chemistry 20220326 5

Pseudouridine, one major RNA modification, is catabolized into uracil and ribose-5'-phosphate by two sequential enzymatic reactions. In the first step, pseudouridine kinase (PUKI) phosphorylates pseudouridine to pseudouridine 5'-monophosphate. High-fidelity catalysis of pseudouridine by PUKI prevents possible disturbance of in vivo pyrimidine homeostasis. However, the molecular basis of how PUKI selectively phosphorylates pseudouridine over uridine with >100-fold greater efficiency despite minor ...[more]

PMID: 35346685

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Project description:Allosteric cooperativity between ATP and substrates is a prominent characteristic of the cAMP-dependent catalytic (C) subunit of protein kinase A (PKA). Not only this long-range synergistic action is involved in substrate recognition and fidelity, but it is likely to regulate PKA association with regulatory subunits and other binding partners. To date, a complete understanding of the molecular determinants for this intramolecular mechanism is still lacking. Here, we used an integrated NMR-restrained molecular dynamics simulations and a Markov Model to characterize the free energy landscape and conformational transitions of the catalytic subunit of protein kinase A (PKA-C). We found that the apo-enzyme populates a broad free energy basin featuring a conformational ensemble of the active state of PKA-C (ground state) and other basins with lower populations (excited states). The first excited state corresponds to a previously characterized inactive state of PKA-C with the αC helix swinging outward. The second excited state displays a disrupted hydrophobic packing around the regulatory (R) spine, with a flipped configuration of the F100 and F102 residues at the tip of the αC-β4 loop. To experimentally validate the second excited state, we mutated F100 into alanine and used NMR spectroscopy to characterize the binding thermodynamics and structural response of ATP and a prototypical peptide substrate. While the activity of PKA-CF100A toward a prototypical peptide substrate is unaltered and the enzyme retains its affinity for ATP and substrate, this mutation rearranges the αC-β4 loop conformation interrupting the allosteric coupling between nucleotide and substrate. The highly conserved αC-β4 loop emerges as a pivotal element able to modulate the synergistic binding between nucleotide and substrate and may affect PKA signalosome. These results may explain how insertion mutations within this motif affect drug sensitivity in other homologous kinases.

Dataset Information

Substrate-binding loop interactions with pseudouridine trigger conformational changes that promote catalytic efficiency of pseudouridine kinase PUKI.

Publications

Substrate-binding loop interactions with pseudouridine trigger conformational changes that promote catalytic efficiency of pseudouridine kinase PUKI.

Similar Datasets

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