PDBsum entry 1ea0

Oxidoreductase

PDB id: 1ea0

Contents

Protein chains

1452 a.a. *

Ligands

OMT ×2

FMN ×2

AKG ×2

F3S ×2

* Residue conservation analysis

PDB id:

1ea0

Name:

Oxidoreductase

Title:

Alpha subunit of a. Brasilense glutamate synthase

Structure:

Glutamate synthase [nadph] large chain. Chain: a, b. Synonym: glutamate synthase alpha subunit, NADPH-gogat, glts alpha chain. Engineered: yes

Source:

Azospirillum brasilense. Organism_taxid: 192. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

3.00Å R-factor: 0.256 R-free: 0.287

Authors:

C.Binda,R.T.Bossi,M.A.Vanoni,A.Mattevi

Key ref:

C.Binda et al. (2000). Cross-talk and ammonia channeling between active centers in the unexpected domain arrangement of glutamate synthase. Structure, 8, 1299-1308. PubMed id: 11188694 DOI: 10.1016/S0969-2126(00)00540-2

Date:

02-Nov-00 Release date: 01-Nov-01

Protein chains

Q05755  (GLTB_AZOBR) -  Glutamate synthase [NADPH] large chain from Azospirillum brasilense

Seq: 1515 a.a.

Struc: 1452 a.a.

Enzyme reactions

• Enzyme class: E.C.1.4.1.13 - glutamate synthase (NADPH).
• Reaction: 2 L-glutamate + NADP⁺ = L-glutamine + 2-oxoglutarate + NADPH + H⁺

2 × L-glutamate + NADP(+) = L-glutamine (Bound ligand (Het Group name = AKG) corresponds exactly) + 2-oxoglutarate + NADPH + H(+)

• Cofactor: FAD; FMN; Iron-sulfur

FAD FMN (Bound ligand (Het Group name = FMN) corresponds exactly) Iron-sulfur

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

reference

DOI no: 10.1016/S0969-2126(00)00540-2

Structure 8:1299-1308 (2000)

PubMed id: 11188694

Cross-talk and ammonia channeling between active centers in the unexpected domain arrangement of glutamate synthase.

C.Binda, R.T.Bossi, S.Wakatsuki, S.Arzt, A.Coda, B.Curti, M.A.Vanoni, A.Mattevi.

ABSTRACT

INTRODUCTION: The complex iron-sulfur flavoprotein glutamate synthase catalyses the reductive synthesis of L-glutamate from 2-oxoglutarate and L-glutamine, a reaction in the plant and bacterial pathway for ammonia assimilation. The enzyme functions through three distinct active centers carrying out L-glutamine hydrolysis, conversion of 2-oxoglutarate into L-glutamate, and electron uptake from an electron donor. RESULTS: The 3.0 A crystal structure of the dimeric 324 kDa core protein of a bacterial glutamate synthase was solved by the MAD method, using the very weak anomalous signal of the two 3Fe-4S clusters present in the asymmetric unit. The 1,472 amino acids of the monomer fold into a four-domain architecture. The two catalytic domains have canonical Ntn-amidotransferase and FMN binding (beta/alpha)8 barrel folds, respectively. The other two domains have an unusual "cut (beta/alpha)8 barrel" topology and an unexpected novel beta-helix structure. Channeling of the ammonia intermediate is brought about by an internal tunnel of 31 A length, which runs from the site of L-glutamine hydrolysis to the site of L-glutamate synthesis. CONCLUSIONS: The outstanding property of glutamate synthase is the ability to coordinate the activity of its various functional sites to avoid wasteful consumption of L-glutamine. The structure reveals two polypeptide segments that connect the catalytic centers and embed the ammonia tunnel, thus being ideally suited to function in interdomain signaling. Depending on the enzyme redox and ligation states, these signal-transducing elements may affect the active site geometry and control ammonia diffusion through a gating mechanism.

Selected figure(s)

Figure 1.
Figure 1. Scheme of the Overall Reaction Catalyzed by the a Subunit of A. brasilense GltS

The above figure is reprinted by permission from Cell Press: Structure (2000, 8, 1299-1308) copyright 2000.

Figure was selected by the author.