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Role of lysine methylation in the activities of elongation factor 1 alpha
1Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
Abstract:
Previous work in our laboratory has demonstrated that 19% of the lysine residues in the protein synthesis elongation factor (EF-1 alpha) are methylated when the factor is purified from the mycelial form of the fungus Mucor racemosus. However, the same factor, when purified from spores of M. racemosus, is largely unmethylated. Despite its wide-spread occurrence in a great number of basic proteins, the functional significance of lysine N-methylation remains poorly understood. Spore and mycelial forms of EF-1 alpha were therefore compared in a series of assays to determine their relative affinities for various substrates and cofactors known to interact with the factor during the elongation cycle. The results suggested that hypomethylated and fully methylated EF-1 alpha had equal affinities for GTP, aminoacyl-tRNA, and ribosomes. Also, methylation did not appear to affect the accuracy of translation in an in vitro system. However, experiments did suggest that methylation may affect the ability of the factor to form complexes with other subunits (EF-1 beta gamma) which are known to enhance the overall rate of protein synthesis.
Insights
Lysine methylation in the protein synthesis elongation factor (EF-1 alpha) from Mucor racemosus does not affect substrate binding or translation accuracy. However, methylation may influence complex formation with EF-1 beta gamma subunits.
Area of Science:
- Molecular Biology
- Biochemistry
- Fungal Biology
Background:
- Lysine N-methylation is a common post-translational modification in basic proteins, but its functional significance is largely unknown.
- The protein synthesis elongation factor 1 alpha (EF-1 alpha) from Mucor racemosus exhibits differential lysine methylation between its mycelial (19% methylated) and spore (unmethylated) forms.
Purpose of the Study:
- To investigate the functional impact of lysine N-methylation on EF-1 alpha.
- To compare the substrate and cofactor affinities of methylated and unmethylated EF-1 alpha.
- To assess the effect of methylation on translation accuracy and complex formation with EF-1 beta gamma.
Main Methods:
- Comparative biochemical assays were performed on purified EF-1 alpha from M. racemosus mycelia and spores.
- Assays measured the binding affinities of EF-1 alpha for GTP, aminoacyl-tRNA, and ribosomes.
- In vitro translation systems were used to evaluate translation accuracy and complex formation with EF-1 beta gamma subunits.
Main Results:
- Methylated and hypomethylated EF-1 alpha showed equivalent affinities for GTP, aminoacyl-tRNA, and ribosomes.
- Lysine methylation did not alter the accuracy of translation in the in vitro system.
- Evidence suggests that methylation may influence the interaction of EF-1 alpha with the EF-1 beta gamma subunits.
Conclusions:
- Lysine N-methylation of EF-1 alpha in Mucor racemosus does not appear to be critical for substrate binding or translational fidelity.
- The differential methylation observed between fungal life forms might regulate protein synthesis rates through modulation of EF-1 alpha complex formation with EF-1 beta gamma subunits.