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Loch JI, Worsztynowicz P, Sliwiak J, Grzechowiak M, Imiolczyk B, Pokrywka K, Chwastyk M, Gilski M, Jaskolski M. Rhizobium etli has two L-asparaginases with low sequence identity but similar structure and catalytic center. Acta Crystallogr D Struct Biol 2023; 79:S2059798323005648. [PMID: 37494066 DOI: 10.1107/s2059798323005648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/26/2023] [Indexed: 07/27/2023] Open
Abstract
The genome of Rhizobium etli, a nitrogen-fixing bacterial symbiont of legume plants, encodes two L-asparaginases, ReAIV and ReAV, that have no similarity to the well characterized enzymes of class 1 (bacterial type) and class 2 (plant type). It has been hypothesized that ReAIV and ReAV might belong to the same structural class 3 despite their low level of sequence identity. When the crystal structure of the inducible and thermolabile protein ReAV was solved, this hypothesis gained a stronger footing because the key residues of ReAV are also present in the sequence of the constitutive and thermostable ReAIV protein. High-resolution crystal structures of ReAIV now confirm that it is a class 3 L-asparaginase that is structurally similar to ReAV but with important differences. The most striking differences concern the peculiar hydration patterns of the two proteins, the presence of three internal cavities in ReAIV and the behavior of the zinc-binding site. ReAIV has a high pH optimum (9-11) and a substrate affinity of ∼1.3 mM at pH 9.0. These parameters are not suitable for the direct application of ReAIV as an antileukemic drug, although its thermal stability and lack of glutaminase activity would be of considerable advantage. The five crystal structures of ReAIV presented in this work allow a possible enzymatic scenario to be postulated in which the zinc ion coordinated in the active site is a dispensable element. The catalytic nucleophile seems to be Ser47, which is part of two Ser-Lys tandems in the active site. The structures of ReAIV presented here may provide a basis for future enzyme-engineering experiments to improve the kinetic parameters for medicinal applications.
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Affiliation(s)
- Joanna I Loch
- Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University, Krakow, Poland
| | | | - Joanna Sliwiak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Marta Grzechowiak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Barbara Imiolczyk
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Kinga Pokrywka
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Mateusz Chwastyk
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Miroslaw Gilski
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Mariusz Jaskolski
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
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Cristóvão JS, Figueira AJ, Carapeto AP, Rodrigues MS, Cardoso I, Gomes CM. The S100B Alarmin Is a Dual-Function Chaperone Suppressing Amyloid-β Oligomerization through Combined Zinc Chelation and Inhibition of Protein Aggregation. ACS Chem Neurosci 2020; 11:2753-2760. [PMID: 32706972 DOI: 10.1021/acschemneuro.0c00392] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Amyloid beta (Aβ) aggregation and imbalance of metal ions are major hallmarks of Alzheimer's disease (AD). Indeed, amyloid plaques of AD patients are enriched in zinc and Aβ42, and AD related-cognitive decline is dependent on extracellular zinc concentration. In vitro, zinc induces the formation of polymorphic Aβ42 oligomers that delay the formation of amyloid fibers at the expense of increased cellular toxicity. S100B is an inflammatory alarmin and one of the most abundant proteins in the brain and is upregulated in AD and associated with amyloid plaques, where it exerts extracellular functions. Recent findings have uncovered novel neuroprotective functions for S100B as a suppressor of Aβ aggregation and toxicity and in the regulation of zinc homeostasis in neurons. Here we combine biophysical and kinetic approaches to demonstrate that such S100B protective functions converge, making the protein a dual-function chaperone capable of suppressing the formation of toxic Aβ oligomers through both chelation of zinc and inhibition of protein aggregation. From detailed kinetic analysis of Aβ42 aggregation monitoring ThT fluorescence, we show that substoichiometric S100B prevents the formation of toxic off-pathway oligomers that are formed by monomeric Aβ42 in the presence of zinc. Indeed, S100B is effective when added during the lag and transition phases of Aβ42 aggregation, and its action under these circumstances results from its ability to buffer zinc, as it perfectly mimics the effect obtained with the chelating agent EDTA. Further, bioimaging analysis combining transmission electron microscopy and atomic force microscopy confirms that catalytic amounts of S100B partly revert the formation of toxic oligomers. Taken together these results indicate a new role for S100B as a dual chaperone whose distinct functions are interrelated and depend on the relative levels of zinc, S100B, and Aβ, which dynamically evolve during AD.
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Affiliation(s)
- Joana S. Cristóvão
- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
| | - António J. Figueira
- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
| | - Ana P. Carapeto
- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
- Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
| | - Mário S. Rodrigues
- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
- Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
| | - Isabel Cardoso
- i3S−Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto 4150-180, Portugal
- IBMC−Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal
| | - Cláudio M. Gomes
- Biosystems & Integrative Sciences Institute, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
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