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Developmental fall in whole body protein turnover of chick embryos during incubation
Insights
Chick embryo development shows a significant decrease in protein synthesis and degradation rates. This decline is linked to increased protein content, impacting the RNA:protein ratio during incubation.
Area of Science:
- Developmental Biology
- Biochemistry
- Animal Physiology
Background:
- Understanding protein turnover is crucial for comprehending embryonic development.
- Previous research has not fully elucidated changes in protein synthesis and degradation rates during avian embryonic growth.
Purpose of the Study:
- To investigate the changes in fractional rates of protein synthesis and degradation in chick embryos during development.
- To determine the relationship between RNA content, protein content, and protein synthesis rates during embryonic growth.
Main Methods:
- Whole body protein turnover was assessed in chick embryos using stable isotopically labeled [15N]phenylalanine.
- Isotope enrichment in free and protein-bound phenylalanine was measured via gas chromatography-mass spectrometry at 12 and 19 days of incubation.
- RNA:protein ratios were analyzed to correlate with synthesis and degradation rates.
Main Results:
- A significant reduction in fractional rates of protein synthesis and degradation was observed in chick embryos between days 12 and 19 of incubation.
- Protein synthesis per unit of RNA remained relatively constant, indicating no change in the translational efficiency of RNA.
- The RNA:protein ratio decreased significantly (by one-third) during this developmental period.
Conclusions:
- The observed decline in fractional protein synthesis rate during chick embryonic development is primarily attributed to an increase in overall protein content.
- The reduction in the RNA:protein ratio directly correlates with the decreased fractional synthesis rate.
- These findings highlight the regulatory mechanisms governing protein metabolism during rapid embryonic growth.
Abstract:
Whole body protein turnover was measured in chick embryos during incubation to investigate whether or not there is a fall in fractional rates of protein synthesis and degradation during development. Stable isotopically labelled [15N]phenylalanine was injected intraperitoneally into embryos on days 12 and 19. From 60 to 90 min after injection the isotope enrichment in free and protein-bound phenylalanine was measured with a selected-ion gas-chromatograph mass-spectrometer. The results showed that from days 12 to 19 of incubation, there was a remarkable reduction in fractional rates of protein synthesis and degradation in the whole body of chick embryos. During embryonic growth, protein synthesis per unit of RNA that is, the minimum amino acid translation rate of RNA, did not change significantly, whereas the RNA:protein ratio was reduced to one-third from days 12 to 19 of incubation. It was concluded, therefore, that the dramatic fall in fractional synthesis rate in chick embryos would be entirely attributable to the rapid increase in protein content, thereby changing the RNA:protein ratio in parallel with the fractional synthesis rate.