Domain

Rab-GTPase-TBC domain (IPR000195)

Short name: Rab-GTPase-TBC_dom

Domain relationships

None.

Description

The ~200 amino acid TBC/rab GTPase-activating protein (GAP) domain is well conserved across species and has been found in a wide range of different proteins from plant adhesion molecules to mammalian oncogenes. The name TBC derives from the name of the murine protein Tbc1 in which this domain was first identified based on its similarity to sequences in the tre-2 oncogene, and the yeast regulators of mitosis, BUB2 and cdc16 [PMID: 7566974]. The connection of this domain with rab GTPase activation stems from subsequent in-depth sequence analyses and alignments [PMID: 9255064] and recent work demonstrating that it appears to contain the catalytic activities of the yeast rab GAPs, GYP1, and GYP7 [PMID: 10508155].

The TBC/rab GAP domain has also been named PTM after three proteins known to contain it: the Drosophila pollux, the human oncoprotein TRE17 (oncoTRE17), and a myeloid cell line-expressed protein [PMID: 8654926]. The TBC/rab GAP domain contains six conserved motifs named A to F [PMID: 9255064]. A conserved arginine residue in the sequence motif B has been shown to be critical for the full GAP activity [PMID: 10508155]. Resolution of the 3D structure of the TBC/rab GAP domain of GYP1 has shown that it is a fully alpha-helical V-shaped molecule. The conserved arginine residue is positioned at the side of the narrow cleft on the concave site of the V-shaped molecule. It has been proposed that this cleft is the binding site for the GTPase. The conserved arginine residue probably functions as a catalytic arginine finger analogous to that seen in ras and Rho-GAPs. The two key features of the arginine finger activation mechanism appear to be (i) the positioning of the catalytically essential GTPase glutamine side chain via a hydrogen bonding interaction between the glutamine carbamoyl-NH2 group and the main chain carbonyl group of the GAP arginine, and (ii) the polarization of the gamma-phosphate group or the stabilization of charge on it via the interaction of the positively charged side chain guanidinoyl group of the GAP arginine [PMID: 11013213].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
SMART
Pfam
PROSITE profiles