Structure of the N-terminal ankyrin repeat domain of the TRPV2 ion channel

The TRPV ion channels mediate responses to many sensory stimuli including heat, low pH, neuropeptides, and chemical ligands. All TRPV subfamily members contain an intracellular N-terminal ankyrin repeat domain (ARD), a prevalent protein interaction motif. The 1.6-A crystal structure of the TRPV2-ARD, with six ankyrin repeats, reveals several atypical structural features. Repeats one through three display unusually long and flexible fingers with a large number of exposed aromatic residues, whereas repeats five and six have unusually long outer helices. Furthermore, a large counterclockwise twist observed in the stacking of repeats four and five breaks the regularity of the domain, altering the shape of surfaces available for interactions with proteins or other cellular ligands. Both solution studies and crystal packing interactions indicate that the TRPV2-ARD does not form homo-oligomers, suggesting that the ARD of TRPV ion channels may be used for interactions with regulatory factors rather than in promoting tetrameric assembly of the ion channels.