6MGT

Crystal structure of alpha-Amino-beta-Carboxymuconate-epsilon-Semialdehyde Decarboxylase Mutant H110A

Summary for 6MGT

• Entry DOI: 10.2210/pdb6mgt/pdb
• Descriptor: 2-amino-3-carboxymuconate 6-semialdehyde decarboxylase, COBALT (II) ION (3 entities in total)
• Functional Keywords: holo structure, decarboxylase, lyase
• Biological source: Pseudomonas fluorescens
• Total number of polymer chains: 2
• Total formula weight: 79418.40

Authors

Yang, Y.,Daivs, I.,Matsui, T.,Rubalcava, I.,Liu, A. (deposition date: 2018-09-14, release date: 2019-06-19, Last modification date: 2023-10-11)

Primary citation

Yang, Y.,Davis, I.,Matsui, T.,Rubalcava, I.,Liu, A.
Quaternary structure of alpha-amino-beta-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) controls its activity.
J.Biol.Chem., 294:11609-11621, 2019

PubMed Abstract: α-Amino-β-carboxymuconate-ϵ-semialdehyde decarboxylase (ACMSD) plays an important role in l-tryptophan degradation via the kynurenine pathway. ACMSD forms a homodimer and is functionally inactive as a monomer because its catalytic assembly requires an arginine residue from a neighboring subunit. However, how the oligomeric state and self-association of ACMSD are controlled in solution remains unexplored. Here, we demonstrate that ACMSD from can self-assemble into homodimer, tetramer, and higher-order structures. Using size-exclusion chromatography coupled with small-angle X-ray scattering (SEC-SAXS) analysis, we investigated the ACMSD tetramer structure, and fitting the SAXS data with X-ray crystal structures of the monomeric component, we could generate a pseudo-atomic structure of the tetramer. This analysis revealed a tetramer model of ACMSD as a head-on dimer of dimers. We observed that the tetramer is catalytically more active than the dimer and is in equilibrium with the monomer and dimer. Substituting a critical residue of the dimer-dimer interface, His-110, altered the tetramer dissociation profile by increasing the higher-order oligomer portion in solution without changing the X-ray crystal structure. ACMSD self-association was affected by pH, ionic strength, and other electrostatic interactions. Alignment of ACMSD sequences revealed that His-110 is highly conserved in a few bacteria that utilize nitrobenzoic acid as a sole source of carbon and energy, suggesting a dedicated functional role of ACMSD's self-assembly into the tetrameric and higher-order structures. These results indicate that the dynamic oligomerization status potentially regulates ACMSD activity and that SEC-SAXS coupled with X-ray crystallography is a powerful tool for studying protein self-association.

PubMed: 31189654
DOI: 10.1074/jbc.RA119.009035

Experimental method

X-RAY DIFFRACTION (2.77 Å)