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Methylation of ribosomal proteins during ribosome assembly in Escherichia coli
Abstract:
In Escherichia coli, a number of ribosomal proteins are methylated. The time of methylation of L7 and L11 during ribosome assembly was studied. It was observed that the methylation of L7 could occur in the free protein stage. Both the 32S and 40S ribonucleoprotein intermediates also contained methylated L7 although the extent of methylation in these particles was not as high as in the free L7, the 45S or the 50S particles. Free L11 could also be partially methylated but the bulk of methylation of this protein was found in the 45S and the 50S particles. It was previously reported that the methylation of L7 is inversely proportional to the growth temperature (Chang 1978), we now show that once L7 is methylated at 25 degree, the methyl group is stable when the culture is shifted to 37 degree C. However, a partial turnover of the methyl group of L7 is observed when the methylated ribosome is chased at 25 degree C. On the other hand, the methyl groups of L11 appear to be stable at either 25 degree C or 37 degree C. We also observe that the extent of methylation of both L7 and L11 stays nearly constant during the cell growth cycle from early log to stationary phase.
Insights
Methylation of ribosomal proteins L7 and L11 in Escherichia coli occurs at different stages of ribosome assembly. Methyl groups on L7 are stable at higher temperatures, while L11 methylation is stable across temperatures.
Area of Science:
- Molecular Biology
- Bacterial Ribosome Biogenesis
- Post-translational Modifications
Background:
- Ribosomal proteins undergo post-translational modifications, including methylation, which can affect ribosome function.
- Understanding the timing and stability of these modifications is crucial for comprehending ribosome assembly and cellular regulation.
Purpose of the Study:
- To investigate the temporal dynamics of methylation for ribosomal proteins L7 and L11 during ribosome assembly in Escherichia coli.
- To determine the stability of methyl groups on L7 and L11 under different temperature conditions and during the cell growth cycle.
Main Methods:
- Analysis of methylation status of L7 and L11 in free proteins and various ribonucleoprotein intermediates (32S, 40S, 45S, 50S).
- Temperature shift experiments (25°C to 37°C and vice versa) to assess methyl group stability.
- Monitoring methylation levels across different growth phases (log to stationary).
Main Results:
- Methylation of L7 can occur on free protein and is present in various assembly intermediates, with highest levels in 45S and 50S particles.
- Methylation of L11 primarily occurs in 45S and 50S particles.
- Methyl groups on L7 are stable when shifted from 25°C to 37°C but show partial turnover at 25°C.
- Methyl groups on L11 are stable at both 25°C and 37°C.
- Methylation levels of L7 and L11 remain relatively constant throughout the cell growth cycle.
Conclusions:
- Ribosomal proteins L7 and L11 exhibit distinct methylation patterns during ribosome biogenesis in Escherichia coli.
- The stability of methyl groups on L7 and L11 differs, with L11 methylation being more robust across temperature changes.