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Physical studies on the H3/H4 histone tetramer
Biochemistry
|June 1, 1976
Summary
The (H3/H4)2 tetramer from calf thymus exhibits tertiary structure elements, as revealed by proton magnetic resonance spectroscopy. This protein tetramer can be denatured and renatured, showing distinct hydrodynamic properties compared to globular proteins.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- The (H3/H4)2 tetramer is a key component of chromatin structure.
- Understanding its tertiary structure is crucial for elucidating DNA packaging and gene regulation.
Purpose of the Study:
- To investigate the tertiary structure and hydrodynamic properties of the (H3/H4)2 tetramer.
- To determine the structural changes upon denaturation and renaturation.
Main Methods:
- High-resolution proton magnetic resonance spectroscopy (270 MHz)
- Circular dichroism (CD) and infrared (IR) spectroscopies
- Ultracentrifugation (sedimentation velocity) studies
Main Results:
- The tetramer contains approximately 29% alpha helix and lacks beta structure.
- Proton NMR spectra revealed perturbed resonances not present in individual H3 or H4 proteins, indicating tertiary structure.
- The protein denatures in 6 M urea and can be renatured by dialysis.
- Sedimentation velocity studies showed a frictional ratio of 1.99, suggesting a non-globular hydrodynamic shape.
Conclusions:
- The (H3/H4)2 tetramer possesses elements of tertiary structure.
- The tetramer exhibits distinct hydrodynamic properties, differing from globular proteins.
- The protein demonstrates reversible denaturation, highlighting its structural flexibility.