The structure of the EF-Tu . GDP . Me2+ complex

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Elongation factor (EF-Tu) is essential for protein synthesis, mediating the delivery of aminoacyl-tRNAs to the ribosome.
• Understanding the precise interactions of EF-Tu with guanosine diphosphate (GDP) and metal ions is key to elucidating its mechanism of action.

Purpose of the Study:

• To investigate the structural and chemical interactions within the MgGDP complex at the active site of elongation factor (EF-Tu).
• To determine the coordination of metal ions and the role of different GDP phosphates in EF-Tu binding.

Main Methods:

• Utilized phosphorothioate analogs of guanosine diphosphate (GDP), including GDP[alpha S] and GDP[beta S].
• Employed electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopy.
• Incorporated 17O isotopic labeling to probe specific phosphate interactions.

Main Results:

• EF-Tu exhibits high stereoselectivity for GDP diastereomers, independent of the metal ion, due to alpha-phosphate interaction.
• Metal ion coordination in the EF-Tu . Me2+ . GDP complex occurs primarily with the beta-phosphate of GDP.
• NMR studies reveal stronger Mg2+ interaction with the beta-phosphate than the alpha-phosphate, with the protein binding the beta-phosphorous via two oxygens.

Conclusions:

• The beta-phosphate of GDP is the primary site of metal ion coordination and protein interaction within the EF-Tu active site.
• These findings provide detailed insights into the structural basis of EF-Tu's function in translation elongation.