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Stoichiometry of polypeptide chain elongation
The Journal of Biological Chemistry
|March 25, 1976
Summary
This study quantifies guanosine triphosphate (GTP) hydrolysis during protein synthesis. Each amino acid incorporated into a growing polypeptide chain requires two molecules of GTP to be hydrolyzed.
Area of Science:
- Molecular Biology
- Biochemistry
- Protein Synthesis
Background:
- Polypeptide chain elongation is a fundamental biological process.
- Guanosine triphosphate (GTP) hydrolysis is known to be involved in protein synthesis.
- Precise quantification of GTP consumption during elongation is crucial for understanding translation efficiency.
Purpose of the Study:
- To develop an in vitro system for accurately measuring GTP hydrolysis during polypeptide chain elongation.
- To determine the stoichiometric relationship between amino acid incorporation and GTP consumption.
Main Methods:
- Development of an in vitro system using purified Escherichia coli polysomes.
- Washing polysomes with 1 M NH4Cl to remove endogenous GTPase activities.
- Depletion of subunits and free ribosomes to minimize uncoupled GTP hydrolysis.
Main Results:
- The developed system allows for amino acid incorporation into nascent peptide chains.
- Background GTP hydrolysis was measured and corrected for.
- A precise ratio was established: 2 molecules of GTP hydrolyzed per incorporated amino acid molecule.
Conclusions:
- The study successfully quantitated GTP hydrolysis during polypeptide elongation.
- The findings establish a stoichiometric ratio of 2:1 (GTP hydrolyzed:amino acid incorporated).
- This provides critical quantitative data for models of translational efficiency in E. coli.