7XUY

Crystal structure of 5-chloro-2-hydroxymuconate tautomerase CnbG

Summary for 7XUY

• Entry DOI: 10.2210/pdb7xuy/pdb
• Descriptor: Tautomerase (2 entities in total)
• Functional Keywords: catechol meta-cleavage pathway, beta-alpha-beta block, chloronitrobenzene degradation, hexamer, isomerase
• Biological source: Comamonas testosteroni CNB-1
• Total number of polymer chains: 1
• Total formula weight: 8111.26

Authors

Ma, H.L.,Li, D.F. (deposition date: 2022-05-20, release date: 2023-03-29, Last modification date: 2023-11-29)

Primary citation

Ma, H.L.,Ding, M.,Guo, L.,Li, D.F.
Structural insights into the substrate specificity of 5-chloro-2-hydroxymuconate tautomerase CnbG.
Biochem.Biophys.Res.Commun., 620:42-48, 2022

PubMed Abstract: The catechol meta-cleavage pathway is widely involved in the degradation of aromatic compounds, including those halogenated aromatic hydrocarbons and their derivatives. CnbG is a kind of 4-oxalocrotonate tautomerase (4-OT) located in the catechol meta-cleavage pathway, catalyzes the ketonization of cis,cis-5-chloro-2-hydroxymuconate and cis,cis-2-hydroxymuconate to yield 5-chloro-2-oxo-3-hexene-1,6-dioate and 2-oxo-3-hexene-1,6-dioate, and contributes to the degradation of 4-chloronitrobenzene and chlorobenzene in Comamonas testosteroni CNB-1. Yet, the reason why CnbG and those 4-OTs could recognize various substrates is not well explained. Here, we determined the crystal structure of CnbG at resolution of 2.0 Å and identified that the potential substrate pocket involved in four conserved residues, residues Pro1, Arg11, Arg39 and Trp50, but not five conserved residues as those reported in other 4-OTs. We also found the four conserved residues assemble different sequence patterns in different 4-OTs, indicating their potential roles in catalysis and substrate binding. Via molecular docking, we found the 5-chloro group was clamped by two residues and extended to the solvent, indicating a substrate binding mode that could bear the substitution of different groups in the 5-position. Our work extends the knowledge of the substrate specificity of enzymes in the catechol meta-cleavage pathway.

PubMed: 35777133
DOI: 10.1016/j.bbrc.2022.06.058

Experimental method

X-RAY DIFFRACTION (2.001 Å)