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Structural basis for the allosteric pathway of 4-amino-4-deoxychorismate synthase
Yusuke Nakamichi1, Jyumpei Kobayashi2, Koichi Toyoda2
1Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
Acta Crystallographica. Section D, Structural Biology
|September 15, 2023
Summary
4-Amino-4-deoxychorismate synthase (ADCS) is regulated by allosteric mechanisms. Researchers determined the crystal structure of a bifunctional enzyme, revealing a unique dimer structure essential for ADCS activity and regulation.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- 4-Amino-4-deoxychorismate synthase (ADCS) is a crucial enzyme composed of PabA and PabB subunits.
- ADCS regulates chorismate utilization through allosteric mechanisms between PabA and PabB, but the exact mechanism is unknown due to the lack of complex structure.
- Understanding ADCS allosteric regulation is vital for comprehending metabolic pathways and potential drug targets.
Purpose of the Study:
- To elucidate the allosteric mechanism of ADCS by determining the crystal structure of a bifunctional enzyme.
- To characterize the structural and functional properties of the Streptomyces venezuelae PapA (SvPapA) enzyme.
- To identify key residues and structural features involved in ADCS activity and regulation.
Main Methods:
- X-ray crystallography to determine the 3D structure of SvPapA.
- Enzyme activity assays to measure ADCS function with different substrates and cofactors.
- Structural analysis to identify substrate-binding sites and conformational changes.
Main Results:
- The crystal structure of SvPapA revealed a unique dimeric complex where PabA and PabB domains from different monomers form an active site.
- Chorismate binding induces structural changes in the PabB domain, facilitating substrate recognition and catalysis.
- Mg2+ binding site and PabA domain conformation are modulated by chorismate presence, indicating a dynamic allosteric regulation mechanism.
- SvPapA exhibits ADCS activity using glutamate or ammonium as amino donors in the presence of Mg2+.
Conclusions:
- The study reveals the first crystal structure of a functional ADCS complex, providing atomic-level insights into its unique dimeric organization.
- Structural and functional data elucidate the molecular basis of allosteric regulation in ADCS, highlighting the interplay between chorismate binding and enzyme conformation.
- These findings offer a foundation for understanding ADCS function in vivo and for designing targeted inhibitors.
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