ABCMdb

ABCC8 p.Gln1178Arg

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Publications

PMID: 18281290 [PubMed] Babenko AP et al: "A novel ABCC8 (SUR1)-dependent mechanism of metabolism-excitation uncoupling."

No. Sentence Comment

67 The more significant (p Ͻ 0.005) effect of the mutation at these higher MgATP/ADP ratios indicates that the Q1178R markedly amplifies the stimulatory action of [MgATP] Ͼ 0.5 mM (see later). Login to comment
84 Consistent with the latter report and my model, I hypothesize that the Q1178R mutation reduces the ability of the sulfonylurea-binding TM domain to destabilize the magnesium⅐nucleotide-bound state of the receptor. Login to comment

PMID: 22451668 [PubMed] Ortiz D et al: "Two neonatal diabetes mutations on transmembrane helix 15 of SUR1 increase affinity for ATP and ADP at nucleotide binding domain 2."

No. Sentence Comment

9 Glibenclamide (GBC), a sulfonylurea, was used as a conformational probe to compare nucleotide action on wild type versus Q1178R and R1182Q SUR1 mutants. Login to comment
13 The KD for ATP4d1a; is b03;1 versus 12 mM, Q1178R versus wild type, respectively. Login to comment
14 The linkage constant is b03;10, implying that outward facing conformations bind GBC with a lower affinity, 9-10 nM for Q1178R. Login to comment
17 An eight-state model describes linkage between diazoxide and ATP4d1a; binding; diazoxide markedly increases the affinity of Q1178R for ATP4d1a; and ATP4d1a; augments diazoxide binding. Login to comment
47 Here we focus on two mutations, Q1178R and R1182Q, located in the 15th helix (transmembrane helix) of the second transmembrane domain (TMD2). Login to comment
48 These substitutions are in a cluster of mutations that cause either neonatal diabetes (Q1178R, R1182Q, and A1184E) or hyperinsulinism (C1174F and S1185A). Login to comment
58 The results imply that outward facing conformations with dimerized NBDs bind GBC and diazoxide with low and high affinity, respectively, and that the enhanced stimulatory action of Q1178R and R1182Q is due to their increased affinity for ATP and ADP. Login to comment
101 Table 1 and Table S1 compare the dissociation constants, determined from saturation binding data, for the WT, Q1178R, and R1182Q aporeceptors (i.e. without nucleotides). Login to comment
105 Q1178R and R1182Q Neonatal Diabetes Mutations Potentiate Negative Allosteric Action of MgATP on GBC Binding to SUR1-To assess quantitatively the effect of MgATP on GBC binding, membranes were incubated with increasing ATP concentrations maintained constant by a regenerating system (34); the level of ATP was constant over the 30-min time period of the incubation, as determined using luciferase assays (supplemental Fig. S1). Login to comment
107 The IC50 values for MgATP are b03;850, 37, and 19 òe;M for the WT, R1182Q, and Q1178R receptors, respectively, an increase in the apparent affinity of SUR1Q1178R for ATP of b03;45-fold. Login to comment
109 Q1178R and R1182Q Receptors Have Higher Affinity for ATP4afa; than WT-All ABC proteins have Walker-type nucleotide binding sites whose physiologic substrate is MgATP. Login to comment
115 In terms of an enzyme-substrate model where hydrolysis is blocked, the results show that the mutant receptors have at least a 10-fold greater affinity for ATP4afa; , with Q1178R having a somewhat higher affinity than R1182Q (Tables 2 and S2). Login to comment
117 Simplified Allosteric Model-Previous studies using affinity labeling with 8-N3-[32 P]ATP show that NBD1 has a dissociation constant for NBD1 in the low micromolar range in the absence of Mg2af9; (18), confirmed below for WT and Q1178R receptors. Login to comment
139 E, neonatal diabetes (Q1178R in red and R1182Q in green) and hyperinsulinemia (C1174F in blue) causing mutations are clustered on transmembrane helix 15 (yellow), which feeds into NBD1 (light gray). Login to comment
143 Values are means afe; S.E. SUR1 KG nM WT 0.25 afe; 0.02 Q1178R 1.0 afe; 0.1 R1182Q 0.50 afe; .15 SUR1 Nucleotide Affinities in Neonatal Diabetes 17988 JOURNAL OF BIOLOGICAL CHEMISTRY VOLUME 287ߦNUMBER 22ߦMAY 25, 2012 equation for the four-state model can be expressed as a simple binding isotherm (see supplemental material), G afd; ᐵGᐶ ᐵGᐶ af9; Kobs (Eq. 4) where Kobs, the apparent dissociation constant at a specified concentration of ATP4afa; , is given by the following: Kobs afd; betaKG ᐳᐵTᐶ af9; KTᐴ ᐳᐵTᐶ af9; betaKTᐴ (Eq. 5) Kobs values at increasing concentrations of ATP4afa; were determined by homologous competition experiments (Fig. 3, A-D) and used to estimate KT and beta. Login to comment
146 To determine if the Q1178R mutation affects binding at NBD1, WT and SUR1Q1178R receptors were labeled with 8-N3-[ॹ-32 P]ATP plus increasing unlabeled ATP4afa; . Login to comment
148 The results indicate the Q1178R mutation somewhat reduces the apparent affinity of NBD1 for ATP4afa; , but NBD1 will be nearly saturated in both WT and SUR1Q1178R before there is a significant effect of ATP4afa; on GBC binding (compare Figs. Login to comment
156 A, the curves through the data are logistic equations with IC50 values of 849 afe; 195, 37 afe; 13, and 19 afe; 7 òe;M for WT, R1182Q, and Q1178R, respectively. Login to comment
163 The allosteric and ATP4afa; dissociation constants (beta/KD) (òe;M) are 14/12,200, 6.8/1250, and 9.3/1000 for the WT, R1182Q, and Q1178R receptors, respectively. Login to comment
166 TABLE 2 KT and beta values for WT and neonatal diabetes SUR1 are shown d1e; S.E. (p values in parentheses) SUR1 beta KT òe;M WT 14 afe; 10 (0.2) 12,200 afe; 4030 (0.02) R1182Q 6.8 afe; 0.9 (b0d;0.001) 1250 afe; 258 (0.003) Q1178R 9.3 afe; 1.8 (b0d;0.001) 1000 afe; 179 (b0d;0.001) Q1178R (Kobs method) 10.5 afe; 0.8 (0.005) 846 afe; 142 (0.03) SUR1 Nucleotide Affinities in Neonatal Diabetes MAY 25, 2012ߦVOLUME 287ߦNUMBER 22 JOURNAL OF BIOLOGICAL CHEMISTRY 17989 An eight-state model that describes the linkage between the diazoxide, GBC, and nucleotide binding sites under equilibrium, non-hydrolysis conditions is given in Fig. 5. Login to comment
192 Q1178R Receptor Has Higher Affinity for MgADP and ADP3afa; -MgADP stimulates KATP channel activity (49-53). Login to comment
199 Q1178R retains a high affinity for ATP at NBD1. Login to comment
205 B, example autoradiograms comparing the labeling of WT and Q1178R receptors. Login to comment
228 The WT and Q1178R data and curves are taken from Fig. 2B. Login to comment
232 The IC50 values are 146 afe; 47 and 24 afe; 3 òe;M for WT and Q1178R, respectively. Login to comment
233 Mg2af9; strongly potentiates ADP binding; ADP3afa; has a small, but significant, effect on Q1178R above 10 mM, but no detectable effect on WT at 100 mM. Login to comment
241 The use of a simplified equilibrium model with binding of a single ATP is justified by the finding that the Q1178R substitution has only minor effects on the binding of ATP4afa; to NBD1. Login to comment

PMID: 23665564 [PubMed] Ortiz D et al: "Reinterpreting the action of ATP analogs on K(ATP) channels."

No. Sentence Comment

81 The E1507Q and Q1178R substitutions do not have large effects on the affinities of the apo-receptors for GBC, given by the dissociation constants (KG), which are determined in independent experiments (Table 1). Login to comment
89 Dashed curves are fits to a logistic equation used to estimate the IC50 values (in òe;M): WT: 1163 afe; 439, slope afd; 0.8 afe; 0.1; Q1178R: 17 afe; 3, slope afd; 0.8 afe; 0.1; E1507Q: 2.7 afe; 0.4, slope afd; 0.8 afe; 0.1. Login to comment
92 The parameters are KT afd; 1 òe;M and beta afd; 40 with a defined valueforKG afd;0.63nM.B,theeffectofATP4afa; onGBCbinding.Thecurvesarethebest fitstothefour-statemodel.TheparametersareKT afd;94,2550,and13,400òe;Mandbetaafd; 40,9.2,and15.1withKGdefinedas0.63,1.0,and0.25nM,forE1507Q,Q1178R,andWT, respectively. Login to comment
94 TABLE 1 Binding parameters (KG, IC50, and KT values) for WT, Q1178R, and E1507Q KG values are nM; all IC50 and KT values are òe;M. Login to comment
96 KG IC50 KT MgATP MgADP MgATP (beta) ATP4d1a; (beta) MgATPॹS (beta) ATPॹS4d1a; (beta) WT 0.25 afe; 0.02 1163 afe; 439 161 afe; 28 - 13,400 afe; 3360 (15.1 afe; 9.4) - - Q1178R 1.0 afe; 0.1 17 afe; 3 25 afe; 2 - 2550 afe; 290 (9.2 afe; 1.4) - - E1507Q 0.63 afe; 0.16 2.7 afe; 0.4 - 1 afe; 0.2 (40 afe; 3) 94 afe; 8 (40 afe; 1) 29 afe; 7 (11.6 afe; 3) 234 afe; 31 (3.2 afe; 0.1) Action of ATP Analogs on SUR1 18896 four-state model. Login to comment
135 The solid lines are fits to a logistic equation: IC50 values: WT: 161 afe; 28, slope afd; 1.7 afe; 0.4; Q1178R: 25 afe; 2, slope afd; 1.5 afe; 0.1. Login to comment
193 Substi- TABLE 2 Binding parameters (S0.5 and K1, K2, and KA values) for Q1178R and E1507Q Values are òe;M; K1 and K2, the affinities for MgATP at NBD1 and NBD2, respectively and KA, the affinity for MgAMP-PNP at NBD1, were estimated using an eight-state model. Login to comment
195 SUR1 S0.5 K1 K2 KA MgAMP-PNP MgAMP-PCP AMP-PNP4d1a; Q1178R 530 afe; 124 - - - - - E1507Q 573 afe; 103 3360 afe; 410 31100 afe; 2240 0.7 afe; 0.2 1.5 afe; 0.1 1.2 afe; 0.2 FIGURE 5. Login to comment

PMID: 25926814 [PubMed] Ortiz D et al: "Neonatal Diabetes and Congenital Hyperinsulinism Caused by Mutations in ABCC8/SUR1 are Associated with Altered and Opposite Affinities for ATP and ADP."

No. Sentence Comment

122 to the current regulatory model, both E1506 substitutions have reduced affinity for MgADP (Figure 4), consistent with electrophysiological data demonstrating that SUR1E1506D/Kir6.2 and 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 0.0 0.2 0.4 0.6 0.8 1.0 E1506Q Q1178R E1506D R1182Q I1424V WT S1185A C1174F E1506K G1479R Specific Bound GBC [MgATP] (&#b5;M) 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 0.0 0.2 0.4 0.6 0.8 1.0 E1506Q E1506K Q1178R I1424V E1506D R1182Q WT S1185A C1174F G1479R Specific Bound GBC [ATP 4- ] (&#b5;M) B A FIGURE 3 | Comparison of nucleotide-induced conformational switching in WT and SUR1 mutants. Login to comment
128 To support this hypothesis we analyzed additional mutations including I1424V (ND) and G1479R (CHI) in NBD2 and a cluster of disease causing mutations in TMD2: C1174F (CHI), S1185A (CHI), Q1178R (ND), and R1182Q (ND). Login to comment
151 Figure 5 shows that diazoxide potentiates the 1 10 100 1000 0.0 0.2 0.4 0.6 0.8 1.0 Q1178R I1424V R1182Q S1185A C1174F WT E1506Q E1506D G1479R E1506K Specific Bound GBC [MgADP] (&#b5;M) FIGURE 4 | MgADP-induced conformational switching in WT and SUR1 mutants. Login to comment