6LPI

Crystal Structure of AHAS holo-enzyme

Summary for 6LPI

• Entry DOI: 10.2210/pdb6lpi/pdb
• Descriptor: Acetolactate synthase isozyme 1 small subunit, Acetolactate synthase isozyme 1 large subunit, FLAVIN-ADENINE DINUCLEOTIDE, ... (6 entities in total)
• Functional Keywords: ahas, allosteric regulation, recombination
• Biological source: Escherichia coli (strain K12); More
• Total number of polymer chains: 8
• Total formula weight: 301487.30

Authors

Zhang, Y.,Yang, X.,Xi, Z.,Shen, Y. (deposition date: 2020-01-10, release date: 2020-11-18, Last modification date: 2023-11-29)

Primary citation

Zhang, Y.,Li, Y.,Liu, X.,Sun, J.,Li, X.,Lin, J.,Yang, X.,Xi, Z.,Shen, Y.
Molecular architecture of the acetohydroxyacid synthase holoenzyme.
Biochem.J., 477:2439-2449, 2020

PubMed Abstract: The acetohydroxyacid synthase (AHAS) holoenzyme catalyzes the first step of branch-chain amino acid biosynthesis and is essential for plants and bacteria. It consists of a regulatory subunit (RSU) and a catalytic subunit (CSU). The allosteric mechanism of the AHAS holoenzyme has remained elusive for decades. Here, we determined the crystal structure of the AHAS holoenzyme, revealing the association between the RSU and CSU in an A2B2 mode. Structural analysis in combination with mutational studies demonstrated that the RSU dimer forms extensive interactions with the CSU dimer, in which a conserved salt bridge between R32 and D120 may act as a trigger to open the activation loop of the CSU, resulting in the activation of the CSU by the RSU. Our study reveals the activation mechanism of the AHAS holoenzyme.

PubMed: 32538427
DOI: 10.1042/BCJ20200292

Experimental method

X-RAY DIFFRACTION (2.849 Å)