Mutational analysis of the TRE2 oncogene encoding an inactive RabGAP.

Area of Science:

• Molecular Biology
• Oncology
• Protein Biochemistry

Background:

• The TRE2 oncoprotein shares structural similarity with the RabGAP (GTPase-activating protein) family.
• Despite structural homology, TRE2 exhibits enzymatic inactivity, a key characteristic differentiating it from functional RabGAPs.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the enzymatic inactivity of the TRE2 oncoprotein.
• To identify specific regions and residues responsible for TRE2's lack of GTPase-activating protein activity.

Main Methods:

• Hydrophobic cluster analysis of the TRE2 oncoprotein sequence.
• Secondary structure prediction and receptor-binding domain analysis.
• Site-directed and random mutagenesis experiments.

Main Results:

• The TBC domain, typically the active site in RabGAPs, is non-functional in TRE2.
• A 93-amino acid region C-terminal to the TBC domain also contributes significantly to TRE2's inactivity.
• Mutagenesis studies identified key residues involved in the loss of function.

Conclusions:

• The lack of secondary structure in the C-terminal region flanking the TBC domain is hypothesized to be crucial for TRE2's enzymatic inactivity.
• This structural feature may inhibit GAP activity even if the TBC domain itself were potentially functional.