1hh1: Difference between revisions

[[Image:1hh1.gif|left|200px]]<br /><applet load="1hh1" size="350" color="white" frame="true" align="right" spinBox="true"  

The 2.15-A structure of Hjc, a Holliday junction-resolving enzyme from the archaeon Sulfolobus solfataricus, reveals extensive structural homology with a superfamily of nucleases that includes type II restriction enzymes. Hjc is a dimer with a large DNA-binding surface consisting of numerous basic residues surrounding the metal-binding residues of the active sites. Residues critical for catalysis, identified on the basis of sequence comparisons and site-directed mutagenesis studies, are clustered to produce two active sites in the dimer, about 29 A apart, consistent with the requirement for the introduction of paired nicks in opposing strands of the four-way DNA junction substrate. Hjc displays similarity to the restriction endonucleases in the way its specific DNA-cutting pattern is determined but uses a different arrangement of nuclease subunits. Further structural similarity to a broad group of metal/phosphate-binding proteins, including conservation of active-site location, is observed. A high degree of conservation of surface electrostatic character is observed between Hjc and T4-phage endonuclease VII despite a complete lack of structural homology. A model of the Hjc-Holliday junction complex is proposed, based on the available functional and structural data.

1HH1 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Sulfolobus_solfataricus Sulfolobus solfataricus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HH1 OCA].  

[[Category: Bond, C S.]]

[[Category: Hunter, W N.]]

[[Category: White, M F.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:01:10 2008''