TY - JOUR
T1 - Conserved water-mediated hydrogen bond network between TM-I, -II, -VI, and -VII in 7TM receptor activation
AU - Nygaard, Rie
AU - Hansen, Louise Valentin
AU - Mokrosinski, Jacek
AU - Frimurer, Thomas M
AU - Schwartz, Thue W
N1 - Keywords: Amino Acid Motifs; Animals; COS Cells; Cercopithecus aethiops; DNA Mutational Analysis; Hydrogen Bonding; Ligands; Models, Biological; Molecular Conformation; Mutagenesis; Protein Structure, Tertiary; Receptors, Adrenergic, beta-2; Receptors, G-Protein-Coupled; Signal Transduction; Water
PY - 2010/6/18
Y1 - 2010/6/18
N2 - Five highly conserved polar residues connected by a number of structural water molecules together with two rotamer microswitches, TrpVI:13 and TyrVII:20, constitute an extended hydrogen bond network between the intracellular segments of TM-I, -II, -VI, and -VII of 7TM receptors. Molecular dynamics simulations showed that, although the fewer water molecules in rhodopsin were relatively movable, the hydrogen bond network of the β2-adrenergic receptor was fully loaded with water molecules that were surprisingly immobilized between the two rotamer switches, both apparently being in their closed conformation. Manipulations of the rotamer state of TyrVII:20 and TrpVI:13 demonstrated that these residues served as gates for the water molecules at the intracellular and extracellular ends of the hydrogen bond network, respectively. TrpVI:13 at the bottom of the main ligand-binding pocket was shown to apparently function as a catching trap for water molecules. Mutational analysis of the β2-adrenergic receptor demonstrated that the highly conserved polar residues of the hydrogen bond network were all important for receptor signaling but served different functions, some dampening constitutive activity (AsnI:18, AspII:10, and AsnVII:13), whereas others (AsnVII:12 and Asn-VII:16) located one helical turn apart and sharing a water molecule were shown to be essential for agonist-induced signaling. It is concluded that the conserved water hydrogen bond network of 7TM receptors constitutes an extended allosteric interface between the transmembrane segments being of crucial importance for receptor signaling and that part of the function of the rotamer micro-switches, TyrVII:20 and TrpVI:13, is to gate or trap the water molecules.
AB - Five highly conserved polar residues connected by a number of structural water molecules together with two rotamer microswitches, TrpVI:13 and TyrVII:20, constitute an extended hydrogen bond network between the intracellular segments of TM-I, -II, -VI, and -VII of 7TM receptors. Molecular dynamics simulations showed that, although the fewer water molecules in rhodopsin were relatively movable, the hydrogen bond network of the β2-adrenergic receptor was fully loaded with water molecules that were surprisingly immobilized between the two rotamer switches, both apparently being in their closed conformation. Manipulations of the rotamer state of TyrVII:20 and TrpVI:13 demonstrated that these residues served as gates for the water molecules at the intracellular and extracellular ends of the hydrogen bond network, respectively. TrpVI:13 at the bottom of the main ligand-binding pocket was shown to apparently function as a catching trap for water molecules. Mutational analysis of the β2-adrenergic receptor demonstrated that the highly conserved polar residues of the hydrogen bond network were all important for receptor signaling but served different functions, some dampening constitutive activity (AsnI:18, AspII:10, and AsnVII:13), whereas others (AsnVII:12 and Asn-VII:16) located one helical turn apart and sharing a water molecule were shown to be essential for agonist-induced signaling. It is concluded that the conserved water hydrogen bond network of 7TM receptors constitutes an extended allosteric interface between the transmembrane segments being of crucial importance for receptor signaling and that part of the function of the rotamer micro-switches, TyrVII:20 and TrpVI:13, is to gate or trap the water molecules.
U2 - 10.1074/jbc.M110.106021
DO - 10.1074/jbc.M110.106021
M3 - Journal article
C2 - 20395291
SN - 0021-9258
VL - 285
SP - 19625
EP - 19636
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 25
ER -