Related Experiment Video
Updated: Aug 11, 2026
16:24
Analyzing and Building Nucleic Acid Structures with 3DNA
Published on: April 26, 2013
HMG-D complexed to a bulge DNA: an NMR model
Summary
This study presents an NMR model of the HMG-D protein bound to a distorted DNA structure. The findings reveal how HMG proteins recognize and bind to deformed DNA junctions, specifically the dA(2) DNA bulge.
Area of Science:
- Structural Biology
- Biochemistry
- Molecular Biophysics
Background:
- High-mobility group (HMG) proteins are crucial in DNA binding and architectural roles.
- Drosophila HMG-D is a functional counterpart to mammalian HMG1/2 proteins.
- Understanding HMG-DNA interactions is key to deciphering gene regulation.
Purpose of the Study:
- To determine the structural model of the Drosophila HMG-D protein complexed with a dA(2) DNA bulge.
- To elucidate the recognition mechanism of HMG proteins for deformed DNA structures.
- To investigate the binding interface between HMG-D and the DNA bulge.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study the HMG-D/DNA complex.
- Chemical shift and linewidth footprinting were used to identify the binding interface.
- Computational modeling generated an ensemble of structures using NMR-derived constraints.
- Nuclear Overhauser Effect (NOE) enhancements were analyzed to map intermolecular contacts.
Main Results:
- The HMG-D protein binds to a dA(2) DNA bulge, a distorted DNA structure.
- The base pair adjacent to the bulge is not formed, a key feature recognized by the protein.
- Intermolecular NOE enhancements indicate interactions between Thr 33 of HMG-D and DNA nucleotides near the bulge.
- The study demonstrates that non-sequence-specific HMG proteins recognize the junction between duplex and nonduplex DNA.
Conclusions:
- The structural model provides insights into HMG protein recognition of DNA structural distortions.
- HMG-D specifically recognizes the junctional DNA structure of the dA(2) bulge.
- This work offers the first experimental evidence for HMG proteins binding to deformed DNA junctions.
Related Concept Videos
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
00:48¹H NMR of Labile Protons: Deuterium (²H) Substitution
This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
01:192D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)
Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
01:182D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.