1ei1

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(New page: 200px<br /><applet load="1ei1" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ei1, resolution 2.3&Aring;" /> '''DIMERIZATION OF E. CO...)
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'''DIMERIZATION OF E. COLI DNA GYRASE B PROVIDES A STRUCTURAL MECHANISM FOR ACTIVATING THE ATPASE CATALYTIC CENTER'''<br />
'''DIMERIZATION OF E. COLI DNA GYRASE B PROVIDES A STRUCTURAL MECHANISM FOR ACTIVATING THE ATPASE CATALYTIC CENTER'''<br />
==Overview==
==Overview==
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DNA-gyrase exhibits an unusual ATP-binding site that is formed as a result, of gyrase B subunit dimerization, a structural transition that is also, essential for DNA capture during the topoisomerization cycle. Previous, structural studies on Escherichia coli DNA-gyrase B revealed that, dimerization is the result of a polypeptidic exchange involving the, N-terminal 14 amino acids. To provide experimental data that dimerization, is critical for ATPase activity and enzyme turnover, we generated mutants, with reduced dimerization by mutating the two most conserved residues of, the GyrB N-terminal arm (Tyr-5 and Ile-10 residues). Our data demonstrate, that the hydrophobic Ile-10 residue plays an important role in enzyme, dimerization and the nucleotide-protein contact mediated by Tyr-5 side, chain residue helps the dimerization process. Analysis of ATPase, activities of mutant proteins provides evidence that dimerization enhances, the ATP-hydrolysis turnover. The structure of the Y5S mutant of the, N-terminal 43-kDa fragment of E. coli DNA GyrB subunit indicates that, Tyr-5 residue provides a scaffold for the ATP-hydrolysis center. We, describe a channel formed at the dimer interface that provides a, structural mechanism to allow reactive water molecules to access the, gamma-phosphate group of the bound ATP molecule. Together, these results, demonstrate that dimerization strongly contributes to the folding and, stability of the catalytic site for ATP hydrolysis. A role for the, essential Mg(2+) ion for the orientation of the phosphate groups of the, bound nucleotide inside the reactive pocket was also uncovered by, superposition of the 5'-adenylyl beta-gamma-imidodiphosphate (ADPNP), wild-type structure to the salt-free ADPNP structure.
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DNA-gyrase exhibits an unusual ATP-binding site that is formed as a result of gyrase B subunit dimerization, a structural transition that is also essential for DNA capture during the topoisomerization cycle. Previous structural studies on Escherichia coli DNA-gyrase B revealed that dimerization is the result of a polypeptidic exchange involving the N-terminal 14 amino acids. To provide experimental data that dimerization is critical for ATPase activity and enzyme turnover, we generated mutants with reduced dimerization by mutating the two most conserved residues of the GyrB N-terminal arm (Tyr-5 and Ile-10 residues). Our data demonstrate that the hydrophobic Ile-10 residue plays an important role in enzyme dimerization and the nucleotide-protein contact mediated by Tyr-5 side chain residue helps the dimerization process. Analysis of ATPase activities of mutant proteins provides evidence that dimerization enhances the ATP-hydrolysis turnover. The structure of the Y5S mutant of the N-terminal 43-kDa fragment of E. coli DNA GyrB subunit indicates that Tyr-5 residue provides a scaffold for the ATP-hydrolysis center. We describe a channel formed at the dimer interface that provides a structural mechanism to allow reactive water molecules to access the gamma-phosphate group of the bound ATP molecule. Together, these results demonstrate that dimerization strongly contributes to the folding and stability of the catalytic site for ATP hydrolysis. A role for the essential Mg(2+) ion for the orientation of the phosphate groups of the bound nucleotide inside the reactive pocket was also uncovered by superposition of the 5'-adenylyl beta-gamma-imidodiphosphate (ADPNP) wild-type structure to the salt-free ADPNP structure.
==About this Structure==
==About this Structure==
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1EI1 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with SO4, ANP and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/DNA_topoisomerase_(ATP-hydrolyzing) DNA topoisomerase (ATP-hydrolyzing)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.99.1.3 5.99.1.3] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1EI1 OCA].
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1EI1 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=ANP:'>ANP</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/DNA_topoisomerase_(ATP-hydrolyzing) DNA topoisomerase (ATP-hydrolyzing)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=5.99.1.3 5.99.1.3] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EI1 OCA].
==Reference==
==Reference==
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[[Category: dimer]]
[[Category: dimer]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 14:00:49 2007''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:27:57 2008''

Revision as of 10:28, 21 February 2008

Image:1ei1.gif

1ei1, resolution 2.3Å

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DIMERIZATION OF E. COLI DNA GYRASE B PROVIDES A STRUCTURAL MECHANISM FOR ACTIVATING THE ATPASE CATALYTIC CENTER

Overview

DNA-gyrase exhibits an unusual ATP-binding site that is formed as a result of gyrase B subunit dimerization, a structural transition that is also essential for DNA capture during the topoisomerization cycle. Previous structural studies on Escherichia coli DNA-gyrase B revealed that dimerization is the result of a polypeptidic exchange involving the N-terminal 14 amino acids. To provide experimental data that dimerization is critical for ATPase activity and enzyme turnover, we generated mutants with reduced dimerization by mutating the two most conserved residues of the GyrB N-terminal arm (Tyr-5 and Ile-10 residues). Our data demonstrate that the hydrophobic Ile-10 residue plays an important role in enzyme dimerization and the nucleotide-protein contact mediated by Tyr-5 side chain residue helps the dimerization process. Analysis of ATPase activities of mutant proteins provides evidence that dimerization enhances the ATP-hydrolysis turnover. The structure of the Y5S mutant of the N-terminal 43-kDa fragment of E. coli DNA GyrB subunit indicates that Tyr-5 residue provides a scaffold for the ATP-hydrolysis center. We describe a channel formed at the dimer interface that provides a structural mechanism to allow reactive water molecules to access the gamma-phosphate group of the bound ATP molecule. Together, these results demonstrate that dimerization strongly contributes to the folding and stability of the catalytic site for ATP hydrolysis. A role for the essential Mg(2+) ion for the orientation of the phosphate groups of the bound nucleotide inside the reactive pocket was also uncovered by superposition of the 5'-adenylyl beta-gamma-imidodiphosphate (ADPNP) wild-type structure to the salt-free ADPNP structure.

About this Structure

1EI1 is a Single protein structure of sequence from Escherichia coli with , and as ligands. Active as DNA topoisomerase (ATP-hydrolyzing), with EC number 5.99.1.3 Full crystallographic information is available from OCA.

Reference

Dimerization of Escherichia coli DNA-gyrase B provides a structural mechanism for activating the ATPase catalytic center., Brino L, Urzhumtsev A, Mousli M, Bronner C, Mitschler A, Oudet P, Moras D, J Biol Chem. 2000 Mar 31;275(13):9468-75. PMID:10734094

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