 |
PDBsum entry 1ea0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Oxidoreductase
|
PDB id
|
|
|
|
1ea0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Cross-Talk and ammonia channeling between active centers in the unexpected domain arrangement of glutamate synthase.
|
|
|
Authors
|
|
C.Binda,
R.T.Bossi,
S.Wakatsuki,
S.Arzt,
A.Coda,
B.Curti,
M.A.Vanoni,
A.Mattevi.
|
|
|
Ref.
|
|
Structure, 2000,
8,
1299-1308.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
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.
|
|
|
|
|
|
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.
|
|
|
|
|
|
|
