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Intra- and interloop interactions in the folded G quartet structure of Oxytricha telomeric sequence
P Balagurumoorthy1, S K Brahmachari
1Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
Indian Journal of Biochemistry & Biophysics
|December 1, 1995
Summary
The Oxytricha telomeric sequence d(G4T4)3G4 forms an antiparallel G-quadruplex structure. Cation type (Na+ vs. K+) influences loop interactions and structural stability, impacting biological functions.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Telomeric sequences form G-quadruplex structures crucial for genome stability.
- The Oxytricha telomeric sequence d(G4T4)3G4 is known to form G-quadruplexes.
- Understanding cation-dependent structural variations is vital for biological context.
Purpose of the Study:
- To establish the antiparallel intramolecular G-quadruplex structure of d(G4T4)3G4.
- To investigate the influence of different cations (Na+, K+) on this structure.
- To discuss the biological implications of cation-induced structural heterogeneity.
Main Methods:
- Spectroscopic methods (Circular Dichroism).
- Chemical probing (KMnO4).
Main Results:
- Established the antiparallel intramolecular G-quadruplex structure of d(G4T4)3G4.
- Observed cation-dependent structural differences, with K+ increasing thermal stability but disrupting loop interactions compared to Na+.
- Identified intra- and interloop interactions in the Na+-induced structure.
Conclusions:
- The d(G4T4)3G4 sequence forms an antiparallel G-quadruplex structure.
- Cation binding significantly alters G-quadruplex conformation and stability.
- Cation-dependent micro-heterogeneity in G-quadruplex loops has potential biological consequences.