1NP3

Crystal structure of class I acetohydroxy acid isomeroreductase from Pseudomonas aeruginosa

Summary for 1NP3

• Entry DOI: 10.2210/pdb1np3/pdb
• Descriptor: Ketol-acid reductoisomerase (2 entities in total)
• Functional Keywords: a deep figure-of-eight knot, c-terminal alpha-helical domain, oxidoreductase
• Biological source: Pseudomonas aeruginosa
• Total number of polymer chains: 4
• Total formula weight: 145866.14

Authors

Ahn, H.J.,Eom, S.J.,Yoon, H.-J.,Lee, B.I.,Cho, H.,Suh, S.W. (deposition date: 2003-01-17, release date: 2003-05-06, Last modification date: 2024-03-13)

Primary citation

Ahn, H.J.,Eom, S.J.,Yoon, H.-J.,Lee, B.I.,Cho, H.,Suh, S.W.
Crystal Structure of Class I Acetohydroxy Acid Isomeroreductase from Pseudomonas aeruginosa
J.Mol.Biol., 328:505-515, 2003

PubMed Abstract: Acetohydroxy acid isomeroreductase (AHIR) is a key enzyme in the biosynthesis of branched-chain amino acids. We have determined the first crystal structure of a class I AHIR from Pseudomonas aeruginosa at 2.0 A resolution. Its dodecameric architecture of 23 point group symmetry is assembled of six dimeric units and dimerization is essential for the formation of the active site. The dimeric unit of P.aeruginosa AHIR partially superimposes with a three-domain monomer of spinach AHIR, a class II enzyme. This demonstrates that the so-called plant-specific insert in the middle of spinach AHIR is structurally and functionally equivalent to the C-terminal alpha-helical domain of P.aeruginosa AHIR, and the C-terminal alpha-helical domain was duplicated during evolution from the shorter, class I AHIRs to the longer, class II AHIRs. The dimeric unit of P.aeruginosa AHIR possesses a deep figure-of-eight knot, essentially identical with that in the spinach AHIR monomer. Thus, our work lowers the likelihood of the previous proposal that "domain duplication followed by exchange of a secondary structure element can be a source of such a knot in the protein structure" being correct.

PubMed: 12691757
DOI: 10.1016/S0022-2836(03)00264-X

Experimental method

X-RAY DIFFRACTION (2 Å)