Tunable paramagnetic relaxation enhancements by [Gd(DPA)(3)] (3-) for protein structure analysis

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Nuclear Magnetic Resonance Spectroscopy

Background:

• Paramagnetic relaxation enhancements (PRE) are crucial for obtaining structural insights in protein and protein-ligand complex studies using nuclear magnetic resonance (NMR).
• Conventional PRE methods often require covalent attachment of reagents, limiting accessibility and flexibility.
• The gadolinium-dipicolinic acid complex, [Gd(DPA)3]3-, offers a non-covalent, site-specific alternative for PRE applications.

Purpose of the Study:

• To introduce and validate a novel non-covalent method for site-specific PRE measurements in NMR.
• To demonstrate the utility of the [Gd(DPA)3]3- complex for quantitative distance measurements and structural elucidation.
• To enhance the interpretation of pseudocontact shifts (PCS) induced by lanthanide complexes.

Main Methods:

• Utilized the non-covalent binding of [Gd(DPA)3]3- to proteins to induce PREs.
• Employed varying ratios of [Gd(DPA)3]3- to protein to scale PRE effects.
• Measured distances between nuclear spins and the Gd(3+) ion up to approximately 15 Å.
• Applied the method to determine the quaternary structure of the GCN4 leucine zipper.

Main Results:

• Achieved site-specific PREs using a non-covalent gadolinium complex.
• Demonstrated quantitative distance measurements within 15 Å of the Gd(3+) ion.
• Successfully mapped the metal ion position relative to the protein structure.
• The method accurately enhanced the interpretation of pseudocontact shifts.

Conclusions:

• The [Gd(DPA)3]3- complex provides a versatile and straightforward approach for site-specific PRE measurements in NMR.
• This technique significantly aids in determining protein structures and understanding protein-ligand interactions.
• The method is particularly valuable for enhancing the interpretation of lanthanide-induced pseudocontact shifts.