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1b6r

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{{STRUCTURE_1b6r| PDB=1b6r | SCENE= }}
{{STRUCTURE_1b6r| PDB=1b6r | SCENE= }}
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'''N5-CARBOXYAMINOIMIDAZOLE RIBONUCLEOTIDE SYNTHETASE FROM E. COLI'''
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===N5-CARBOXYAMINOIMIDAZOLE RIBONUCLEOTIDE SYNTHETASE FROM E. COLI===
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==Overview==
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Escherichia coli PurK, a dimeric N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) synthetase, catalyzes the conversion of 5-aminoimidazole ribonucleotide (AIR), ATP, and bicarbonate to N5-CAIR, ADP, and Pi. Crystallization of both a sulfate-liganded and the MgADP-liganded E. coli PurK has resulted in structures at 2.1 and 2.5 A resolution, respectively. PurK belongs to the ATP grasp superfamily of C-N ligase enzymes. Each subunit of PurK is composed of three domains (A, B, and C). The B domain contains a flexible, glycine-rich loop (B loop, T123-G130) that is disordered in the sulfate-PurK structure and becomes ordered in the MgADP-PurK structure. MgADP is wedged between the B and C domains, as with all members of the ATP grasp superfamily. Other enzymes in this superfamily contain a conserved Omega loop proposed to interact with the B loop, define the specificity of their nonnucleotide substrate, and protect the acyl phosphate intermediate formed from this substrate. PurK contains a minimal Omega loop without conserved residues. In the reaction catalyzed by PurK, carboxyphosphate is the putative acyl phosphate intermediate. The sulfate of the sulfate ion-liganded PurK interacts electrostatically with Arg 242 and the backbone amide group of Asn 245, components of the J loop of the C domain. This sulfate may reveal the location of the carboxyphosphate binding site. Conserved residues within the C-terminus of the C domain define a pocket that is proposed to bind AIR in collaboration with an N-terminal strand loop helix motif in the A domain (P loop, G8-L1). The P loop is proposed to bind the phosphate of AIR on the basis of similar binding sites observed in PurN and PurE and proposed in PurD and PurT, four other enzymes in the purine pathway.
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{{ABSTRACT_PUBMED_10569930}}
==About this Structure==
==About this Structure==
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[[Category: Carboxyphosphate]]
[[Category: Carboxyphosphate]]
[[Category: Purine biosynthesis]]
[[Category: Purine biosynthesis]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 18:23:58 2008''

Revision as of 15:24, 30 June 2008

Image:1b6r.png

Template:STRUCTURE 1b6r

N5-CARBOXYAMINOIMIDAZOLE RIBONUCLEOTIDE SYNTHETASE FROM E. COLI

Template:ABSTRACT PUBMED 10569930

About this Structure

1B6R is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Three-dimensional structure of N5-carboxyaminoimidazole ribonucleotide synthetase: a member of the ATP grasp protein superfamily., Thoden JB, Kappock TJ, Stubbe J, Holden HM, Biochemistry. 1999 Nov 23;38(47):15480-92. PMID:10569930

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