The elongation factor Tu . guanosine tetraphosphate complex

Area of Science:

• Molecular Biology
• Bacterial Physiology
• Protein-Nucleic Acid Interactions

Background:

• Elongation factor Tu (EF-Tu) is crucial for bacterial protein synthesis.
• The stringent response is a global regulatory mechanism in bacteria triggered by stress.
• EF-Tu's interaction with guanine nucleotides regulates its function.

Purpose of the Study:

• To investigate the nucleotide-bound state of EF-Tu during the stringent response.
• To determine the functional consequences of EF-Tu complexation with guanosine 5 -diphosphate 3 -diphosphate (ppGpp).

Main Methods:

• Isolation of EF-Tu from Escherichia coli cells undergoing stringent response.
• Anion-exchange chromatography to separate EF-Tu nucleotide complexes.
• Hydrolysis protection experiments to assess ternary complex formation.

Main Results:

• EF-Tu from stringent E. coli predominantly forms a complex with ppGpp.
• This EF-Tu.ppGpp complex is separable from EF-Tu.GDP using anion-exchange chromatography.
• The EF-Tu.ppGpp complex cannot form a ternary complex with aminoacyl-tRNAs, unlike EF-Tu.GTP.

Conclusions:

• The stringent response modifies EF-Tu's nucleotide binding preference.
• ppGpp binding to EF-Tu inhibits its ability to interact with aminoacyl-tRNAs.
• This mechanism likely contributes to the regulation of protein synthesis during stress conditions.