 |
PDBsum entry 2fje
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Oxidoreductase
|
PDB id
|
|
|
|
2fje
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Reaction mechanism of the iron-Sulfur flavoenzyme adenosine-5'-Phosphosulfate reductase based on the structural characterization of different enzymatic states.
|
|
|
Authors
|
|
A.Schiffer,
G.Fritz,
P.M.Kroneck,
U.Ermler.
|
|
|
Ref.
|
|
Biochemistry, 2006,
45,
2960-2967.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The iron-sulfur flavoenzyme adenosine-5'-phosphosulfate (APS) reductase
catalyzes a key reaction of the global sulfur cycle by reversibly transforming
APS to sulfite and AMP. The structures of the dissimilatory enzyme from
Archaeoglobus fulgidus in the reduced state (FAD(red)) and in the sulfite adduct
state (FAD-sulfite-AMP) have been recently elucidated at 1.6 and 2.5 A
resolution, respectively. Here we present new structural features of the enzyme
trapped in four different catalytically relevant states that provide us with a
detailed picture of its reaction cycle. In the oxidized state (FAD(ox)), the
isoalloxazine moiety of the FAD cofactor exhibits a similarly bent conformation
as observed in the structure of the reduced enzyme. In the APS-bound state
(FAD(ox)-APS), the substrate APS is embedded into a 17 A long substrate channel
in such a way that the isoalloxazine ring is pushed toward the channel bottom,
thereby producing a compressed enzyme-substrate complex. A clamp formed by
residues ArgA317 and LeuA278 to fix the adenine ring and the curved APS
conformation appear to be key factors to hold APS in a strained conformation.
This energy-rich state is relaxed during the attack of APS on the reduced FAD. A
relaxed FAD-sulfite adduct is observed in the structure of the FAD-sulfite
state. Finally, a FAD-sulfite-AMP1 state with AMP within van der Waals distance
of the sulfite adduct could be characterized. This structure documents how
adjacent negative charges are stabilized by the protein matrix which is crucial
for forming APS from AMP and sulfite in the reverse reaction.
|
|
|
|
|
|
|
