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The three-dimensional structure of a DNA duplex containing looped-out bases
L Joshua-Tor1, D Rabinovich, H Hope
1Department of Structural Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Nature
|July 7, 1988
Summary
Unpaired bases in DNA can cause mutations and form hairpin loops. This study reveals their structure in a DNA crystal, showing they loop out from a B-DNA duplex with minimal disruption.
Area of Science:
- Molecular Biology
- Structural Biology
- Genetics
Background:
- Unpaired bases in DNA are implicated in frameshift mutagenesis and hairpin loop formation in quasipalindromic sequences.
- Previous studies utilized thermodynamic and Nuclear Magnetic Resonance (NMR) methods to investigate DNA conformation.
Purpose of the Study:
- To determine the crystal structure of a DNA fragment with unpaired bases.
- To elucidate the conformation of unpaired bases within a DNA duplex.
Main Methods:
- Oligonucleotide crystallization.
- X-ray crystallography to determine DNA structure.
- Analysis of DNA duplex conformation.
Main Results:
- The DNA fragment adopted a B-DNA duplex conformation in the crystal state.
- Two adenosine bases were observed to be looped out from the double helix.
- The looped-out bases caused minimal disruption to the overall DNA duplex structure.
Conclusions:
- The crystal structure provides insights into the conformation of unpaired bases in DNA.
- This structural information can contribute to understanding DNA mutagenesis mechanisms.