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Molecular cloning of a novel ras-like protein from chicken
1Laboratorium für Biochemie I, Eidgenössische Technische Hochschule, Zürich, Switzerland.
Abstract:
We have isolated a cDNA clone from a chicken DNA expression library which codes for a ras-like polypeptide of 216 amino acid residues. This polypeptide is closely related to the human protein TC4 and to the yeast protein Spil, two novel proteins that may be involved in the coordination of the cell cycle. In the amino-terminal region, the three polypeptides possess a P-loop motif characteristic of GTP-binding proteins. At the carboxy-terminal end, however, they lack the typical CAAX-box which is usually responsible for membrane anchorage of ras-like proteins. It is therefore likely that the three polypeptides define a new subclass of GTP-binding proteins within the ras-like superfamily.
Insights
Researchers identified a novel ras-like protein in chickens, related to human TC4 and yeast Spil proteins involved in cell cycle coordination. This GTP-binding protein lacks typical membrane anchorage, suggesting a new subclass within the ras-like superfamily.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Ras-like proteins are crucial for cellular signaling and function.
- GTP-binding proteins play key roles in various cellular processes, including the cell cycle.
- Membrane anchorage is a common feature of ras-like proteins, mediating their localization and function.
Purpose of the Study:
- To isolate and characterize novel ras-like proteins from non-mammalian species.
- To investigate the structural and functional relationship of newly identified ras-like proteins to known homologs.
- To determine the potential role of these proteins in cell cycle regulation.
Main Methods:
- Isolation of a cDNA clone from a chicken DNA expression library.
- Amino acid sequence analysis to identify conserved motifs.
- Comparison of the deduced amino acid sequence with known GTP-binding proteins and ras-like proteins.
Main Results:
- A cDNA clone encoding a 216-amino acid ras-like polypeptide was isolated from chicken.
- The chicken polypeptide shows homology to human TC4 and yeast Spil proteins, implicated in cell cycle coordination.
- Both the chicken polypeptide and its homologs (TC4, Spil) possess a GTP-binding P-loop motif but lack the canonical CAAX-box for membrane anchorage.
Conclusions:
- The identified chicken ras-like polypeptide represents a novel protein within the ras-like superfamily.
- The absence of a CAAX-box suggests a distinct mechanism of action or localization compared to canonical ras proteins.
- These findings indicate the existence of a new subclass of GTP-binding proteins potentially involved in cell cycle regulation.