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Contents |
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* Residue conservation analysis
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Enzyme class 2:
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Chains A, B:
E.C.2.7.1.25
- Adenylyl-sulfate kinase.
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Reaction:
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ATP + adenylyl sulfate = ADP + 3'-phosphoadenylyl sulfate
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ATP
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+
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adenylyl sulfate
Bound ligand (Het Group name = )
matches with 90.00% similarity
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=
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ADP
Bound ligand (Het Group name = )
matches with 96.00% similarity
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+
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3'-phosphoadenylyl sulfate
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Enzyme class 3:
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Chains A, B:
E.C.2.7.7.4
- Sulfate adenylyltransferase.
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Reaction:
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ATP + sulfate = diphosphate + adenylyl sulfate
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ATP
Bound ligand (Het Group name = )
matches with 83.00% similarity
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+
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sulfate
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=
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diphosphate
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+
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adenylyl sulfate
Bound ligand (Het Group name = )
matches with 90.00% similarity
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Note, where more than one E.C. class is given (as above), each may
correspond to a different protein domain or, in the case of polyprotein
precursors, to a different mature protein.
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Molecule diagrams generated from .mol files obtained from the
KEGG ftp site
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Gene Ontology (GO) functional annotation
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Biological process
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sulfate assimilation
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1 term
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Biochemical function
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transferase activity, transferring phosphorus-containing groups
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3 terms
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DOI no:
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J Biol Chem
282:22112-22121
(2007)
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PubMed id:
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Structural mechanism for substrate inhibition of the adenosine 5'-phosphosulfate kinase domain of human 3'-phosphoadenosine 5'-phosphosulfate synthetase 1 and its ramifications for enzyme regulation.
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N.Sekulic,
M.Konrad,
A.Lavie.
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ABSTRACT
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In mammals, the universal sulfuryl group donor molecule 3'-phosphoadenosine
5'-phosphosulfate (PAPS) is synthesized in two steps by a bifunctional enzyme
called PAPS synthetase. The APS kinase domain of PAPS synthetase catalyzes the
second step in which APS, the product of the ATP-sulfurylase domain, is
phosphorylated on its 3'-hydroxyl group to yield PAPS. The substrate APS acts as
a strong uncompetitive inhibitor of the APS kinase reaction. We generated
truncated and point mutants of the APS kinase domain that are active but devoid
of substrate inhibition. Structural analysis of these mutant enzymes reveals the
intrasubunit rearrangements that occur upon substrate binding. We also observe
intersubunit rearrangements in this dimeric enzyme that result in asymmetry
between the two monomers. Our work elucidates the structural elements required
for the ability of the substrate APS to inhibit the reaction at micromolar
concentrations. Because the ATP-sulfurylase domain of PAPS synthetase influences
these elements in the APS kinase domain, we propose that this could be a
communication mechanism between the two domains of the bifunctional enzyme.
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Selected figure(s)
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Figure 2.
FIGURE 2. The APS kinase domain consists of three rigid
body parts. A, a ribbon diagram of the dimeric  50N
variant of the APS kinase domain from human PAPSS1 with dADP
(purple) and APS (green) in the active site. Note that both
nucleotides are present only in molecule A, whereas the active
site of the molecule B contains only dADP. The empty phosphoryl
acceptor binding site coincides with the disordered loop between
helix  6 and strand  5in
molecule B. The Rigid Body 1 (RB1) region is shown in light blue
in molecule A and dark blue in molecule B; Rigid Body 2 (RB2) is
yellow in molecule A and orange in molecule B; the APS-cap
regions are pink and red in molecules A and B, respectively. B,
schematic of the 50N APS kinase dimer
presented in the same color scheme as the ribbon diagram in A.
Inset, schematic of an NMP kinase monomer demonstrates its
similarity and difference to that of APS kinase. The three rigid
bodies in NMP kinases are: lid (blue), core (yellow), and NMP
binding region (pink). C, overlay of molecule A and molecule B
of the 50N APS kinase variant
based on C atoms belonging to
residues that define RB1. Note the excellent overlay of RB1, and
the different conformation of RB2 and APS-cap. D, analogous
overlay as in C where C atoms from residues
belonging to RB2 were used for calculating the superposition
matrix. However, the APS-caps do not overlay well. Superposition
of only APS-cap residues demonstrates that the APS-cap also
behaves as a rigid body (inset). Together, C and D demonstrate
the validity of dissecting APS kinase into three rigid bodies.
Colors in C and D correspond to those in A.
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Figure 7.
FIGURE 7. Schematic model for the role of helix 1 in
substrate inhibition. A, in the presence of helix 1 the
APS kinase can adopt a symmetric dimer. In such a state, both
active sites can simultaneously bind APS and ADP, thereby
forming an inhibitory complex. B, enzyme lacking helix 1 adopts
an asymmetrical dimer in which one subunit has a non-functional
APS-binding site. From this state (i), ADP can leave (ii), and
ATP can bind (iii). To the E·ATP complex, the second
substrate APS can bind resulting in a closed conformation for
that monomer (iv). Concomitantly, the APS binding site of the
neighboring molecule becomes non-functional, thereby eliciting
APS release. See text for details.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
22112-22121)
copyright 2007.
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Figures were
selected
by the author.
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