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A helical arch allowing single-stranded DNA to thread through T5 5'-exonuclease
T A Ceska1, J R Sayers, G Stier
1EMBL, Structural Biology Programme, Heidelberg, Germany. ceska@embl.heidelbergde
Nature
|July 4, 1996
Summary
The crystal structure of T5 5'-exonuclease reveals a unique helical arch for DNA binding. This structure supports a threading mechanism for DNA processing, crucial for replication and repair.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- 5 -exonucleases are vital enzymes involved in DNA replication and repair.
- Many 5 -3 -exonucleases exhibit both exonucleolytic and endonucleolytic activities.
- Bacteriophage T5 5 -exonuclease shares similarities with eubacterial DNA polymerases but is encoded separately.
Purpose of the Study:
- To determine the 2.5-A crystal structure of the phage T5 5 -exonuclease.
- To elucidate the mechanism of DNA binding and processing by T5 5 -exonuclease.
Main Methods:
- X-ray crystallography at 2.5-A resolution.
- Structural analysis and molecular modeling.
Main Results:
- The T5 5 -exonuclease structure features a distinctive helical arch for DNA binding.
- A threading mechanism model is proposed, where DNA slides through the arch.
- The active site contains two metal-binding sites crucial for enzymatic activity.
Conclusions:
- The helical arch structure facilitates DNA binding and processing via a threading mechanism.
- Understanding T5 5 -exonuclease structure provides insights into DNA replication and repair mechanisms.
- The structure reveals key features of the active site, including metal-binding sites.