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Mistranslation in cells infected with the bacteriophage MS2: direct evidence of Lys for Asn substitution
Abstract:
The coat protein of the bacteriophage MS2 was found to show an increased level of charge heterogeneity when synthesized in Escherichia coli starved for Asn or Lys. No such increase was found when the host was starved for Arg, His Ile or Pro. This is the pattern predicted by "two-out-of-three" codon misreading in the coat protein gene. In the case of Asn starvation, direct measurements of the relative incorporation of Lys demonstrate that the observed charge heterogeneity is the result of mistranslation. Asn starvation increased the error frequency in coat protein to over 0.3 mistake per asparagine codon. The small amount of charge heterogeneity seen in unstarved cells seems also to be the result of misreading Asn codons.
Insights
Bacterial protein synthesis errors increase when cells lack asparagine (Asn) or lysine (Lys). This charge heterogeneity in MS2 bacteriophage coat protein is due to codon misreading during translation.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Bacteriophage MS2 coat protein synthesis is a model for studying protein production in Escherichia coli.
- Amino acid starvation can impact protein fidelity and lead to mistranslation.
- Codon misreading is a known phenomenon affecting protein synthesis accuracy.
Purpose of the Study:
- To investigate the effect of specific amino acid starvation on the charge heterogeneity of MS2 bacteriophage coat protein.
- To determine if observed charge heterogeneity is a result of "two-out-of-three" codon misreading.
- To quantify the error frequency in coat protein synthesis under Asn starvation.
Main Methods:
- Synthesizing MS2 coat protein in Escherichia coli under starvation conditions for various amino acids (Asn, Lys, Arg, His, Ile, Pro).
- Analyzing the charge heterogeneity of the synthesized coat protein.
- Directly measuring the relative incorporation of lysine during Asn starvation to confirm mistranslation.
Main Results:
- Starvation for Asn or Lys significantly increased charge heterogeneity in MS2 coat protein.
- Starvation for Arg, His, Ile, or Pro did not result in increased charge heterogeneity.
- Asn starvation led to an error frequency exceeding 0.3 mistakes per asparagine codon.
- Even in unstarved cells, some charge heterogeneity was observed, likely due to Asn codon misreading.
Conclusions:
- The "two-out-of-three" codon misreading mechanism explains the observed charge heterogeneity under specific amino acid starvation.
- Asparagine (Asn) codon misreading is a primary cause of charge heterogeneity in MS2 coat protein, even under normal conditions.
- Lysine (Lys) starvation also contributes to protein charge heterogeneity, supporting the role of mistranslation in protein synthesis fidelity.