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Ankyrin Repeat
Domain(ARD) of
TRPV2
By: Marilyn Nguyen
Zebrafish
Human
PDB ID: 2ETC, 2ETA, 2ETB
Summary:
•Part of the Transient Receptor Potential (TRP) cation
channel family and Vanilloid (V) subfamily.
•Vanilloid receptors recognize capaisin. The original
capaisin receptor is TRPV1. TRPV2 is a homologue of
this receptor.
•They are broad range cation channels that are crucial
for processes ranging from sensory signaling to
magnesium homeostasis.
•The channels are selective for calcium and magnesium,
preferring these two cations over sodium ions.
•TRP channels have large N- and C-Terminal cytosolic
regions that are believed to contain many unknown
protein interactions and regulatory motifs.
•N-terminal region of all TRPV channels contain
ankyrin repeats. These repeats are thought to be
essential for the proper functioning of the channel.
They are involved in protein-protein interactions in
bacterial, achaeal, and eukaryotes.
•TRPV2 was discovered in 1999 by David Julius’s
laboratory in the Department of Cellular and
Molecular Pharmacology at the University of
California.
•TRPV2 channels can be found in the central nervous
system, spleen and lung.
•Sequence of TRPV2 is highly conserved among
mammalian species.
Function:
•A thermosensitive receptor that is activated around
52ºC
•Believed to be involved in nerve and sensory responses
to heat, specifically, stimulation of the sensory ganglia.
•Little is known about the true function of the Ankyrin
Repeat Domain (ARD) of TRPV2, but it is suspected to
be involved in cell surface trafficking.
Structure: (Taken from Rattus norvegicus; common name: brown rat)
•Ankyrin Repeats Domain (ARD) monomeric in solution.
•Ankyrin repeats are approximately 33 amino acid
residues in length consisting of two anti-parallel alpha
helices separated by intervening finger loop regions.
•The three-dimensional structure of TRPV2-ARD
consists of 6 ankyrin repeat structure motifs. However,
only 4 of these motifs have been identified.
•TRPV2-ARD is highly conserved between difference
species.
•Ankyrin Repeats 1-3 are long flexible fingers with
several exposed aromatic residues
•Ankyrin Repeats 5-6 have long outer helices (~ 9
residues instead of typical 7 residues).
•Repeats 4-5 exhibits an unusual counterclockwise
twist for stacking. This alters the shape of the surface
and is believed to be an important site for protein or
ligand interaction
•Consists of 5 finger loops that are unique in the fact
that none contain β-hairpin hydrogen bonding in typical
ankyrin repeats.
•2 short anti-parallel helices and a finger loop project
outwards from the helical axes at ~90º angle that
creates an L-shaped cross-section.
•Insertions into ARD are most often observed in the
finger loop regions.
•In humans, Ankyrin groove (ligand recognition site)
has extended loops that are sites of exposed
hydrophobic residues.
Active Site:
•The helical hairpin stacking of the inner helices and
fingers create a concave surface that looks like a
cupped hand. The “palm” region of this concave cupped
hand is considered the active site for protein-protein
interactions
Important residues:
•The concave face of finger loop regions 2 and 3
contain several Phe and Tyr residues that create the
hydrophobic interacting surface.
•Homology to TRPV1 indicates that similar amino acid
residues; Thr, Ser, and Tyr on the concave face of
finger 2 could be phosphorylated through protein
kinase A and Src kinase to play crucial role in
regulation of the channel.
Diseases:
•Muscular Dystrophy – a severe degenerative skeletal
muscle disorder. There are several types of muscular
dystrophy and all are characterized by progressive muscle
weakness. Dystrophy can be caused by a defect in genes
encoding for the dystrophin-glycoprotein complex. This
defect causes lost of membrane integrity and sustained
increase of calcium ion concentration that later results in
muscle degeneration. Mutations in TRPV2 in mice
showed increased number of central nuclei and fiber size
variability/fibrosis/apoptosis and elevated serum creatine
kinase levels, and reduced muscle performance. It is
suggested that TRPV2 is the principal calcium entry route
for the sustained calcium ion concentration increases (2).
References:
1.
2.
3.
Jin X, Touhey J, and Gaudet R. Structure of the N-terminal ankyrin repeat domain
of the TRPV2 ion channel. J. Biol. Chem. 2006 Sep 1;281(35):25006-10.
Iwata Y, Katanosaka Y, Arai Y, Shigekawa M, and Wakabayashi S. Dominantnegative inhibition of Ca2+ influx via TRPV2 ameliorates muscular dystrophy in
animal models. Hum Mol Genet. 2009 Mar 1;18(5):824-34
McCleverty C, Koesema E, Patapoutian A, and Lesley S. Crystal structure of the
human TRPV2 channel ankyrin repeat domain. Protein Science. 2006 Jun
9;15:2201-2206
Alpha Helix (Chain A)
Residues
1
Arg16 - Arg25
2
Leu34 – Asn41
3
Thr58 – Asn66
4
Ile75 – Ser85
5
Ala106 – Lys113
6
Leu116 – Asn125
7
Pro152 – Thr 159
8
Trp162 – Glu170
9
Val188 – Ile 196
10
Pro 200 – Leu 220
11
Pro 237 – Glu 244
12
Glu248 – Glu 257
Beta Sheet (Chain A)
Residues
1
Cys96 – Gly103
2
Ile 229 – Thr236
Hydrophobic region
•Phe 161
•Tyr 162
•Phe 198
•Phe 199
•Phe 207
•Tyr 208
•Phe 209