PDBsum entry 4xeh

Oxidoreductase

PDB id: 4xeh

Contents

Protein chain

327 a.a.

Waters ×101

PDB id:

4xeh

Name:

Oxidoreductase

Title:

Apo structure of kari from ignisphaera aggregans

Structure:

Ketol-acid reductoisomerase. Chain: a. Synonym: acetohydroxy-acid isomeroreductase,alpha-keto-beta- hydroxylacyl reductoisomerase. Engineered: yes

Source:

Ignisphaera aggregans. Organism_taxid: 583356. Strain: dsm 17230 / jcm 13409 / aq1.S1. Gene: ilvc, igag_1561. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

1.39Å R-factor: 0.179 R-free: 0.236

Authors:

J.K.B.Cahn,S.Brinkmann-Chen,F.H.Arnold

Key ref:

J.K.Cahn et al. (2015). Cofactor specificity motifs and the induced fit mechanism in class I ketol-acid reductoisomerases. Biochem J, 468, 475-484. PubMed id: 25849365 DOI: 10.1042/BJ20150183

Date:

23-Dec-14 Release date: 22-Apr-15

Protein chain

E0SRA9  (ILVC_IGNAA) -  Ketol-acid reductoisomerase (NAD(P)(+)) from Ignisphaera aggregans (strain DSM 17230 / JCM 13409 / AQ1.S1)

Seq: 335 a.a.

Struc: 327 a.a.

Enzyme reactions

• Enzyme class: E.C.1.1.1.383 - ketol-acid reductoisomerase [NAD(P)(+)].
• Reaction:
  1. (2R)-2,3-dihydroxy-3-methylbutanoate + NAD⁺ = (2S)-2-acetolactate + NADH + H⁺
  2. (2R)-2,3-dihydroxy-3-methylbutanoate + NADP⁺ = (2S)-2-acetolactate + NADPH + H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1042/BJ20150183

Biochem J 468:475-484 (2015)

PubMed id: 25849365

Cofactor specificity motifs and the induced fit mechanism in class I ketol-acid reductoisomerases.

J.K.Cahn, S.Brinkmann-Chen, T.Spatzal, J.A.Wiig, A.R.Buller, O.Einsle, Y.Hu, M.W.Ribbe, F.H.Arnold.

ABSTRACT

Although most sequenced members of the industrially important ketol-acid reductoisomerase (KARI) family are class I enzymes, structural studies to date have focused primarily on the class II KARIs, which arose through domain duplication. In the present study, we present five new crystal structures of class I KARIs. These include the first structure of a KARI with a six-residue β2αB (cofactor specificity determining) loop and an NADPH phosphate-binding geometry distinct from that of the seven- and 12-residue loops. We also present the first structures of naturally occurring KARIs that utilize NADH as cofactor. These results show insertions in the specificity loops that confounded previous attempts to classify them according to loop length. Lastly, we explore the conformational changes that occur in class I KARIs upon binding of cofactor and metal ions. The class I KARI structures indicate that the active sites close upon binding NAD(P)H, similar to what is observed in the class II KARIs of rice and spinach and different from the opening of the active site observed in the class II KARI of Escherichia coli. This conformational change involves a decrease in the bending of the helix that runs between the domains and a rearrangement of the nicotinamide-binding site.