Cobalt-based paramagnetic probe to study RNA-protein interactions by NMR.

Area of Science:

• Biochemistry
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Paramagnetic resonance enhancement (PRE) is a key NMR technique for elucidating RNA-protein complex structures in solution.
• Conventional PRE methods utilize nitroxide reagents for RNA spin labeling, aiming for minimal structural perturbation.

Purpose of the Study:

• To describe an alternative PRE approach using a Cobalt(II)-based probe for RNA structure determination.
• To demonstrate the utility of this new method for mapping protein contact surfaces.

Main Methods:

• Covalent attachment of a Cobalt(II)-based probe to RNA near the protein binding site via 'click' chemistry.
• Utilizing the probe's paramagnetic properties to attenuate NMR signals from nearby protein residues.
• Correlating signal attenuation extent with probe-residue distance to map protein contact surfaces.

Main Results:

• The Cobalt(II)-based probe effectively attenuates NMR signals from protein residues within a 40Å range.
• The method allows for the construction of a protein contact surface map.
• The approach was successfully applied to study the binding of HIV-1 nucleocapsid protein 7 (NCp7) to a model RNA pentanucleotide.

Conclusions:

• A novel Cobalt(II)-based probe offers a viable alternative to nitroxide spin labels for PRE studies of RNA-protein complexes.
• This 'click' chemistry-based approach facilitates structural mapping of protein-RNA interactions in solution.
• The method provides valuable insights into the structural basis of protein-RNA recognition, exemplified by the NCp7-RNA interaction.