View source for 2avt

[[Image:2avt.gif|left|200px]]<br /><applet load="2avt" size="350" color="white" frame="true" align="right" spinBox="true" 
caption="2avt, resolution 2.0&Aring;" />
'''Crystal structure of the beta subunit from DNA polymerase of Streptococcus pyogenes'''<br />

==Overview==
BACKGROUND: Sliding DNA clamps are processivity factors that are required, for efficient DNA replication. DNA polymerases maintain proximity to, nucleic acid templates by interacting with sliding clamps that encircle, DNA and thereby link the polymerase enzyme to the DNA substrate. Although, the structures of sliding clamps from Gram-negative bacteria (E. coli), eukaryotes, archaea, and T4-like bacteriophages are well-known, the, structure of a sliding clamp from Gram-positive bacteria has not been, reported previously. RESULTS: We have determined the crystal structure of, the dimeric beta subunit of the DNA polymerase III holoenzyme of, Streptococcus pyogenes. The sliding clamp from this Gram-positive organism, forms a ring-shaped dimeric assembly that is similar in overall structure, to that of the sliding clamps from Gram-negative bacteria, bacteriophage, T4, eukaryotes and archaea. The dimer has overall dimensions of, approximately 90 A x approximately 70 A x approximately 25 A with a, central chamber that is large enough to accommodate duplex DNA. In, comparison to the circular shape of other assemblies, the S. pyogenes, clamp adopts a more elliptical structure. CONCLUSION: The sequences of, sliding clamps from S. pyogenes and E. coli are only 23% identical, making, the generation of structural models for the S. pyogenes clamp difficult in, the absence of direct experimental information. Our structure of the S., pyogenes beta subunit completes the catalog of clamp structures from all, the major sequence grouping of sliding clamps. The more elliptical rather, than circular structure of the S. pyogenes clamp implies that the, topological nature of encircling DNA, rather than a precise geometric, shape, is the most conserved aspect for this family of proteins.

==About this Structure==
2AVT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptococcus_pyogenes Streptococcus pyogenes]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AVT OCA]. 

==Reference==
Crystal structure of a DNA polymerase sliding clamp from a Gram-positive bacterium., Argiriadi MA, Goedken ER, Bruck I, O'Donnell M, Kuriyan J, BMC Struct Biol. 2006 Jan 10;6:2. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=16403212 16403212]
[[Category: Single protein]]
[[Category: Streptococcus pyogenes]]
[[Category: Argiriadi, M.A.]]
[[Category: Bruck, I.]]
[[Category: Goedken, E.R.]]
[[Category: Kuriyan, J.]]
[[Category: donnell, M.O.]]
[[Category: beta clamp]]
[[Category: polymerase]]
[[Category: replication]]
[[Category: sliding clamp]]

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