1wet

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{{STRUCTURE_1wet| PDB=1wet | SCENE= }}
{{STRUCTURE_1wet| PDB=1wet | SCENE= }}
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'''STRUCTURE OF THE PURR-GUANINE-PURF OPERATOR COMPLEX'''
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===STRUCTURE OF THE PURR-GUANINE-PURF OPERATOR COMPLEX===
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==Overview==
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The purine repressor, PurR, is the master regulatory protein of de novo purine nucleotide biosynthesis in Escherichia coli. This dimeric transcription factor is activated to bind to cognate DNA operator sites by initially binding either of its physiologically relevant, high affinity corepressors, hypoxanthine (Kd = 9.3 microM) or guanine (Kd = 1.5 microM). Here, we report the 2.5-A crystal structure of the PurR-guanine-purF operator ternary complex and complete the atomic description of 6-oxopurine-induced repression by PurR. As anticipated, the structure of the PurR-guanine-purF operator complex is isomorphous to the PurR-hypoxanthine-purF operator complex, and their protein-DNA and protein-corepressor interactions are nearly identical. The former finding confirms the use of an identical allosteric DNA-binding mechanism whereby corepressor binding 40 A from the DNA-binding domain juxtaposes the hinge regions of each monomer, thus favoring the formation and insertion of the critical minor groove-binding hinge helices. Strikingly, the higher binding affinity of guanine for PurR and the ability of PurR to discriminate against 2-oxopurines do not result from direct protein-ligand interactions, but rather from a water-mediated contact with the exocyclic N-2 of guanine, which dictates the presence of a donor group on the corepressor, and the better electrostatic complementarity of the guanine base and the corepressor-binding pocket.
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(as it appears on PubMed at http://www.pubmed.gov), where 9278422 is the PubMed ID number.
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{{ABSTRACT_PUBMED_9278422}}
==About this Structure==
==About this Structure==
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[[Category: Dna-binding regulatory protein]]
[[Category: Dna-binding regulatory protein]]
[[Category: Repressor]]
[[Category: Repressor]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 07:16:13 2008''

Revision as of 04:16, 29 July 2008

Image:1wet.png

Template:STRUCTURE 1wet

STRUCTURE OF THE PURR-GUANINE-PURF OPERATOR COMPLEX

Template:ABSTRACT PUBMED 9278422

About this Structure

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

Reference

The X-ray structure of the PurR-guanine-purF operator complex reveals the contributions of complementary electrostatic surfaces and a water-mediated hydrogen bond to corepressor specificity and binding affinity., Schumacher MA, Glasfeld A, Zalkin H, Brennan RG, J Biol Chem. 1997 Sep 5;272(36):22648-53. PMID:9278422

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