Mutational Analysis Of The Tre2 Oncogene Encoding An Inactive Rabgap

The TRE2 oncoprotein is structurally related to the RabGAP (GTPase-activating
protein) family. However, TRE2 seems enzymatically inactive. Two regions are
important for its lack of GAP activity. First, the TBC domain, forming the
catalytically active domain of RabGAPs, is non-functional in the oncoprotein.
Also involved in TRE2 inactivity is the 93-aa region flanking the TBC domain on
the C-terminal side. In order to identify the residues responsible for
non-functionality, we performed hydrophobic cluster analysis of the oncoprotein
sequence, combined with secondary structure prediction, receptor-binding domain
analysis, and a tilted peptide calculation. These analyses were complemented with
site-directed and random mutagenesis experiments. On the basis of our data, we
hypothesize that the lack of secondary structure of the region flanking the TBC
domain in TRE2 may explain why this region plays a role in the lack of GAP
activity, even when a potentially functional TBC domain is present.