The long-range electrostatic interactions control tRNA-aminoacyl-tRNA synthetase complex formation

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes in protein synthesis, responsible for charging tRNA molecules with specific amino acids.
• Both aaRSs and their tRNA substrates are typically negatively charged, posing a challenge for specific binding and interaction.

Purpose of the Study:

• To investigate the electrostatic forces driving the initial, long-range attraction between aaRSs and tRNA molecules.
• To understand how these electrostatic interactions overcome the inherent charge repulsion and facilitate complex formation.

Main Methods:

• Numerical solutions of the nonlinear Poisson-Boltzmann equation were employed to calculate the electrostatic potential generated by various aaRSs.
• Three-dimensional (3D) isopotential surfaces were generated at specific contour levels to visualize electrostatic potential distribution.

Main Results:

• Calculated electrostatic potentials revealed large, positively charged patches on different classes of aaRSs (monomers, dimers, heterotetramers).
• These positive potential areas, visualized as 'blue space,' effectively capture negatively charged tRNAs, explaining the long-range attraction.
• The observed electrostatic features remained consistent across a range of contour levels, indicating robustness.

Conclusions:

• Nonspecific electrostatic interactions are the primary drivers of initial 'stickiness' in aaRS-tRNA complexes.
• The positive potential 'blue space' on aaRSs acts as a docking site, guiding tRNAs and overcoming Brownian motion barriers for subsequent specific binding.