1qhh
From Proteopedia
OCA (Talk | contribs)
(New page: 200px<br /><applet load="1qhh" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qhh, resolution 2.5Å" /> '''STRUCTURE OF DNA HELI...)
Next diff →
Revision as of 22:34, 20 November 2007
|
STRUCTURE OF DNA HELICASE 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
1QHH is a Protein complex structure of sequences from Geobacillus stearothermophilus with ATP as ligand. 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 Wed Nov 21 00:41:59 2007
