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PDBsum entry 1kp2
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Substrate induced conformational changes in argininosuccinate synthetase.
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Authors
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C.T.Lemke,
P.L.Howell.
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Ref.
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J Biol Chem, 2002,
277,
13074-13081.
[DOI no: ]
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PubMed id
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Abstract
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Argininosuccinate synthetase (AS) is the rate-limiting enzyme of both the urea
and arginine-citrulline cycles. In mammals, deficiency of AS leads to
citrullinemia, a debilitating and often fatal autosomal recessive urea cycle
disorder, whereas its overexpression for sustained nitric oxide production via
the arginine-citrulline cycle leads to the potentially fatal hypotension
associated with septic and cytokine-induced circulatory shock. The crystal
structures of Escherichia coli argininosuccinate synthetase (EAS) in complex
with ATP and with ATP and citrulline have been determined at 2.0-A resolution.
These are the first EAS structures to be solved in the presence of a nucleotide
substrate and clearly identify the residues that interact with both ATP and
citrulline. Two distinct conformations are revealed for ATP, both of which are
believed to be catalytically relevant. In addition, comparisons of these EAS
structures with those of the apoenzyme and EAS complexed with aspartate and
citrulline (Lemke, C. T., and Howell, P. L. (2001) Structure (Lond.) 9,
1153-1164) provide structural evidence of ATP-induced conformational changes in
the nucleotide binding domain. Combined, these structures also provide
structural explanations of some of the observed kinetic properties of the enzyme
and have enabled a detailed enzymatic mechanism of AS catalysis to be proposed.
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Figure 1.
Fig. 1. The argininosuccinate synthetase mechanism. Step
1, activated citrulline-adenylate is formed, releasing inorganic
pyrophosphate. Step 2, nucleophilic attack by aspartate amino
group forms argininosuccinate and releases AMP.
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Figure 8.
Fig. 8. ATP conformations. The conformations of ATP
observed in lysyl tRNA synthetase (a), EAS ( b), and NAD^+
synthetase (c) are shown. The dashed lines are drawn between the
 -phosphate
of ATP and nucleophile.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
13074-13081)
copyright 2002.
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Secondary reference #1
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Title
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The 1.6 a crystal structure of e. Coli argininosuccinate synthetase suggests a conformational change during catalysis.
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Authors
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C.T.Lemke,
P.L.Howell.
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Ref.
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Structure, 2001,
9,
1153-1164.
[DOI no: ]
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PubMed id
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Figure 2.
Figure 2. EAS Aspartate and Citrulline Binding
Sitess[A]-weighted |F[o]| - |F[c]| omit map contoured at 3s
shows the citrulline (a) and aspartate (c) binding sites.
Schematic representation of the interactions between the protein
and either citrulline (b) or aspartate (d). Dashed lines
represent interactions between atoms, with distances given in Å.
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The above figure is
reproduced from the cited reference
with permission from Cell Press
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