1qhg
From Proteopedia
(New page: 200px<br /><applet load="1qhg" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qhg, resolution 2.50Å" /> '''STRUCTURE OF DNA HEL...) |
|||
| Line 1: | Line 1: | ||
| - | [[Image:1qhg.jpg|left|200px]]<br /><applet load="1qhg" size=" | + | [[Image:1qhg.jpg|left|200px]]<br /><applet load="1qhg" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1qhg, resolution 2.50Å" /> | caption="1qhg, resolution 2.50Å" /> | ||
'''STRUCTURE OF DNA HELICASE MUTANT WITH ADPNP'''<br /> | '''STRUCTURE OF DNA HELICASE MUTANT WITH ADPNP'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Based upon the crystal structures of PcrA helicase, we have made and | + | Based upon the crystal structures of PcrA helicase, we have made and characterised mutations in a number of conserved helicase signature motifs around the ATPase active site. We have also determined structures of complexes of wild-type PcrA with ADPNP and of a mutant PcrA complexed with ADPNP and Mn2+. The kinetic and structural data define roles for a number of different residues in and around the ATP binding site. More importantly, our results also show that there are two functionally distinct conformations of ATP in the active site. In one conformation, ATP is hydrolysed poorly whereas in the other (activated) conformation, ATP is hydrolysed much more rapidly. We propose a mechanism to explain how the stimulation of ATPase activity afforded by binding of single-stranded DNA stabilises the activated conformation favouring Mg2+binding and a consequent repositioning of the gamma-phosphate group which promotes ATP hydrolysis. A part of the associated conformational change in the protein forces the side-chain of K37 to vacate the Mg2+binding site, allowing the cation to bind and interact with ATP. |
==About this Structure== | ==About this Structure== | ||
| - | 1QHG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Geobacillus_stearothermophilus Geobacillus stearothermophilus] with MG and ATP as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1QHG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Geobacillus_stearothermophilus Geobacillus stearothermophilus] with <scene name='pdbligand=MG:'>MG</scene> and <scene name='pdbligand=ATP:'>ATP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QHG OCA]. |
==Reference== | ==Reference== | ||
| Line 13: | Line 13: | ||
[[Category: Geobacillus stearothermophilus]] | [[Category: Geobacillus stearothermophilus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Dillingham, M | + | [[Category: Dillingham, M S.]] |
[[Category: Soultanas, P.]] | [[Category: Soultanas, P.]] | ||
| - | [[Category: Velankar, S | + | [[Category: Velankar, S S.]] |
| - | [[Category: Wigley, D | + | [[Category: Wigley, D B.]] |
[[Category: ATP]] | [[Category: ATP]] | ||
[[Category: MG]] | [[Category: MG]] | ||
| Line 26: | Line 26: | ||
[[Category: sos response]] | [[Category: sos response]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:39:35 2008'' |
Revision as of 12:39, 21 February 2008
|
STRUCTURE OF DNA HELICASE MUTANT WITH ADPNP
Overview
Based upon the crystal structures of PcrA helicase, we have made and characterised mutations in a number of conserved helicase signature motifs around the ATPase active site. We have also determined structures of complexes of wild-type PcrA with ADPNP and of a mutant PcrA complexed with ADPNP and Mn2+. The kinetic and structural data define roles for a number of different residues in and around the ATP binding site. More importantly, our results also show that there are two functionally distinct conformations of ATP in the active site. In one conformation, ATP is hydrolysed poorly whereas in the other (activated) conformation, ATP is hydrolysed much more rapidly. We propose a mechanism to explain how the stimulation of ATPase activity afforded by binding of single-stranded DNA stabilises the activated conformation favouring Mg2+binding and a consequent repositioning of the gamma-phosphate group which promotes ATP hydrolysis. A part of the associated conformational change in the protein forces the side-chain of K37 to vacate the Mg2+binding site, allowing the cation to bind and interact with ATP.
About this Structure
1QHG is a Single protein structure of sequence from Geobacillus stearothermophilus with and as ligands. Full crystallographic information is available from OCA.
Reference
DNA binding mediates conformational changes and metal ion coordination in the active site of PcrA helicase., Soultanas P, Dillingham MS, Velankar SS, Wigley DB, J Mol Biol. 1999 Jul 2;290(1):137-48. PMID:10388562
Page seeded by OCA on Thu Feb 21 14:39:35 2008
