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Cell-free synthesis of the D2-cell adhesion molecule: evidence for three primary translation products
Abstract:
The D2-cell adhesion molecule (D2-CAM) is a membrane glycoprotein that is involved in cell-cell adhesion in the nervous system. To study the biosynthesis of D2-CAM we have translated free and membrane-bound polysomes from rat brain in vitro in the rabbit reticulocyte lysate system. D2-CAM was exclusively synthesized on membrane-bound polysomes. The primary translation products of D2-CAM were three polypeptides of apparent molecular weights 187,000, 134,000, and 112,000. No interconversion between these polypeptides was detected. In contrast to previous suggestions, we conclude that all three D2-CAM polypeptides are primary translation products. When translating polysomes from embryonic and postnatal rat brain, we found that the relative amounts of the three polypeptides synthesized varied with age. Their molecular weights, however, were not age-dependent.
Insights
D2-cell adhesion molecule (D2-CAM) is synthesized on membrane-bound polysomes, producing three distinct polypeptides. Their relative amounts change with age, but molecular weights remain constant, indicating they are primary translation products.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- D2-cell adhesion molecule (D2-CAM) is a key glycoprotein in nervous system cell-cell adhesion.
- Understanding D2-CAM biosynthesis is crucial for comprehending neural development and function.
Purpose of the Study:
- To investigate the biosynthesis of D2-CAM.
- To identify the primary translation products of D2-CAM.
- To determine if D2-CAM polypeptide synthesis is age-dependent.
Main Methods:
- In vitro translation of free and membrane-bound polysomes from rat brain using a rabbit reticulocyte lysate system.
- Analysis of polypeptide molecular weights and potential interconversion.
- Comparison of D2-CAM synthesis in embryonic versus postnatal rat brain polysomes.
Main Results:
- D2-CAM was exclusively synthesized on membrane-bound polysomes.
- Three primary translation products of D2-CAM were identified with molecular weights of 187,000, 134,000, and 112,000.
- No interconversion between these polypeptides was observed.
- The relative amounts of the three D2-CAM polypeptides synthesized varied with age, but their molecular weights were age-independent.
Conclusions:
- All three identified D2-CAM polypeptides are primary translation products, contrary to previous suggestions.
- The age-dependent variation in relative polypeptide amounts suggests developmental regulation of D2-CAM expression.
- These findings provide critical insights into the molecular mechanisms of D2-CAM biosynthesis in the developing nervous system.