ABCC8 p.Lys719Arg
| Predicted by SNAP2: | A: D (91%), C: D (91%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (91%), I: D (95%), L: D (91%), M: D (91%), N: D (95%), P: D (95%), Q: D (91%), R: D (91%), S: D (91%), T: D (91%), V: D (95%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] Mutations in either nucleotide-binding site of P-g... Biochemistry. 1998 Mar 31;37(13):4592-602. Urbatsch IL, Beaudet L, Carrier I, Gros P
Mutations in either nucleotide-binding site of P-glycoprotein (Mdr3) prevent vanadate trapping of nucleotide at both sites.
Biochemistry. 1998 Mar 31;37(13):4592-602., 1998-03-31 [PMID:9521779]
Abstract [show]
Vanadate trapping of nucleotide and site-directed mutagenesis were used to investigate the role of the two nucleotide-binding (NB) sites in the regulation of ATP hydrolysis by P-glycoprotein (mouse Mdr3). Mdr3, tagged with a hexahistidine tail, was overexpressed in the yeast Pichia pastoris and purified to about 90% homogeneity by Ni-affinity chromatography. This protocol yielded purified, reconstituted Mdr3 which exhibited high verapamil stimulation of ATPase activity with a Vmax of 4.2 micromol min-1 mg-1 and a KM of 0.7 mM, suggesting that Mdr3 purified from P. pastoris is highly functional. Point mutations were introduced into the core consensus sequence of the Walker A or B motifs in each of the two NB sites. The mutants K429R, K1072R (Walker A) and D551N, D1196N (Walker B) were functionally impaired and unable to confer cellular resistance to the fungicide FK506 in the yeast Saccharomyces cerevisiae. Single and double mutants (K429R/K1072R, D551N/D1196N) were expressed in P. pastoris, and the effect of these mutations on the ATPase activity of Mdr3 was characterized. Purified reconstituted Mdr3 mutants showed no detectable ATPase activity compared to proteoliposomes purified from negative controls (<5% of wild-type Mdr3). Vanadate readily induced trapping of 8-azido-nucleotide in the wild-type enzyme after a short 10 s incubation, and specific photolabeling of Mdr3 after UV irradiation. No such vanadate-induced trapping/photolabeling was observed in any of the mutants, even after a 60 min trapping period at 37 degrees C. Since vanadate trapping with 8-azido-ATP requires hydrolysis of the nucleotide, the data suggest that 8-azido-ATP hydrolysis is dramatically impaired in all of the mutant proteins (<0.3% activity). These results show that mutations in either NB site prevent single turnover and vanadate trapping of nucleotide in the nonmutant site. These results further suggest that the two NB sites cannot function independently as catalytic sites in the intact molecule. In addition, the N- or C-terminal NB sites appear functionally indistinguishable, and cooperative interactions absolutely required for ATP hydrolysis may originate from both sites.
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No. Sentence Comment
265 Point mutations in the Walker A and B motifs of NB1, K719R, K719M, and D854N impaired 8-azido[R-32 P]ATP binding, whereas NB2 mutations, K1385R, K1385M, and D1506N, retained their ability to bind low concentrations of 8-azido[R-32P]ATP in the presence or absence of Mg2+ (65).
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ABCC8 p.Lys719Arg 9521779:265:53
status: NEW[hide] Molecular aspects of ATP-sensitive K+ channels in ... Pharmacol Ther. 2000 Jan;85(1):39-53. Fujita A, Kurachi Y
Molecular aspects of ATP-sensitive K+ channels in the cardiovascular system and K+ channel openers.
Pharmacol Ther. 2000 Jan;85(1):39-53., [PMID:10674713]
Abstract [show]
ATP-sensitive K+ (K(ATP)) channels are inhibited by intracellular ATP (ATPi) and activated by intracellular nucleoside diphosphates and thus, provide a link between cellular metabolism and excitability. K(ATP) channels are widely distributed in various tissues and may be associated with diverse cellular functions. In the heart, the K(ATP) channel appears to be activated during ischemic or hypoxic conditions, and may be responsible for the increase of K+ efflux and shortening of the action potential duration. Therefore, opening of this channel may result in cardioprotective, as well as proarrhythmic, effects. These channels are clearly heterogeneous. The cardiac K(ATP) channel is the prototype of K(ATP) channels possessing approximately 80 pS of single-channel conductance in the presence of approximately 150 mM extracellular K+ and opens spontaneously in the absence of ATPi. A vascular K(ATP) channel called a nucleoside diphosphate-dependent K+ (K(NDP)) channel exhibits properties significantly different from those of the cardiac K(ATP) channel. The K(NDP) channel has the single-channel conductance of approximately 30-40 pS in the presence of approximately 150 mM extracellular K+, is closed in the absence of ATPi, and requires intracellular nucleoside di- or triphosphates, including ATPi to open. Nevertheless, K(ATP) and K(NDP) channels are both activated by K+ channel openers, including pinacidil and nicorandil, and inhibited by sulfonylurea derivatives such as glibenclamide. It recently was found that the cardiac K(ATP) channel is composed of a sulfonylurea receptor (SUR)2A and a two-transmembrane-type K+ channel subunit Kir6.2, while the vascular K(NDP) channel may be the complex of SUR2B and Kir6.1. By precisely comparing the functional properties of the SUR2A/Kir6.2 and the SUR2B/Kir6.1 channels, we shall show that the single-channel characteristics and pharmacological properties of SUR/Kir6.0 channels are determined by Kir and SUR subunits, respectively, while responses to intracellular nucleotides are determined by both SUR and Kir subunits.
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No. Sentence Comment
567 The high-affinity binding site was saturated with 10 M ATPi in the absence of Mg2ϩ i. Substitution of the conserved lysine residue in the Walker A motif (K719R and K719M) or the aspartate residue in the Walker B motif (D854N) in the first NBF all abolished the high-affinity ATPi-binding, while the corresponding mutations in the second NBF did not cause any significant effect.
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ABCC8 p.Lys719Arg 10674713:567:168
status: NEW568 Because Ueda et al. (1997) and Gribble et al. (1997b) used different mutations (K719R, K719M, or D854N vs. K719A, respectively), it is not clear whether the ATPi binding found by Ueda et al. (1997) underlies the sensitization of Kir6.2 to ATPi by SUR1.
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ABCC8 p.Lys719Arg 10674713:568:80
status: NEW571 The high-affinity binding site was saturated with 10 mM ATPi in the absence of Mg21 i. Substitution of the conserved lysine residue in the Walker A motif (K719R and K719M) or the aspartate residue in the Walker B motif (D854N) in the first NBF all abolished the high-affinity ATPi-binding, while the corresponding mutations in the second NBF did not cause any significant effect.
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ABCC8 p.Lys719Arg 10674713:571:155
status: NEW572 Because Ueda et al. (1997) and Gribble et al. (1997b) used different mutations (K719R, K719M, or D854N vs. K719A, respectively), it is not clear whether the ATPi binding found by Ueda et al. (1997) underlies the sensitization of Kir6.2 to ATPi by SUR1.
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ABCC8 p.Lys719Arg 10674713:572:80
status: NEW[hide] Molecular biology of adenosine triphosphate-sensit... Endocr Rev. 1999 Apr;20(2):101-35. Aguilar-Bryan L, Bryan J
Molecular biology of adenosine triphosphate-sensitive potassium channels.
Endocr Rev. 1999 Apr;20(2):101-35., [PMID:10204114]
Abstract [show]
KATP channels are a newly defined class of potassium channels based on the physical association of an ABC protein, the sulfonylurea receptor, and a K+ inward rectifier subunit. The beta-cell KATP channel is composed of SUR1, the high-affinity sulfonylurea receptor with multiple TMDs and two NBFs, and KIR6.2, a weak inward rectifier, in a 1:1 stoichiometry. The pore of the channel is formed by KIR6.2 in a tetrameric arrangement; the overall stoichiometry of active channels is (SUR1/KIR6.2)4. The two subunits form a tightly integrated whole. KIR6.2 can be expressed in the plasma membrane either by deletion of an ER retention signal at its C-terminal end or by high-level expression to overwhelm the retention mechanism. The single-channel conductance of the homomeric KIR6.2 channels is equivalent to SUR/KIR6.2 channels, but they differ in all other respects, including bursting behavior, pharmacological properties, sensitivity to ATP and ADP, and trafficking to the plasma membrane. Coexpression with SUR restores the normal channel properties. The key role KATP channel play in the regulation of insulin secretion in response to changes in glucose metabolism is underscored by the finding that a recessive form of persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is caused by mutations in KATP channel subunits that result in the loss of channel activity. KATP channels set the resting membrane potential of beta-cells, and their loss results in a constitutive depolarization that allows voltage-gated Ca2+ channels to open spontaneously, increasing the cytosolic Ca2+ levels enough to trigger continuous release of insulin. The loss of KATP channels, in effect, uncouples the electrical activity of beta-cells from their metabolic activity. PHHI mutations have been informative on the function of SUR1 and regulation of KATP channels by adenine nucleotides. The results indicate that SUR1 is important in sensing nucleotide changes, as implied by its sequence similarity to other ABC proteins, in addition to being the drug sensor. An unexpected finding is that the inhibitory action of ATP appears to be through a site located on KIR6.2, whose affinity for ATP is modified by SUR1. A PHHI mutation, G1479R, in the second NBF of SUR1 forms active KATP channels that respond normally to ATP, but fail to activate with MgADP. The result implies that ATP tonically inhibits KATP channels, but that the ADP level in a fasting beta-cell antagonizes this inhibition. Decreases in the ADP level as glucose is metabolized result in KATP channel closure. Although KATP channels are the target for sulfonylureas used in the treatment of NIDDM, the available data suggest that the identified KATP channel mutations do not play a major role in diabetes. Understanding how KATP channels fit into the overall scheme of glucose homeostasis, on the other hand, promises insight into diabetes and other disorders of glucose metabolism, while understanding the structure and regulation of these channels offers potential for development of novel compounds to regulate cellular electrical activity.
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No. Sentence Comment
526 For example, the K719R mutation in the conserved Walker A motif that is involved in binding of the ␣- and beta-phosphates has no effect on the ATP sensitivity of reconstituted channels (190), although Ueda et al. (239) show that SUR1K719R does not photolabel with [32 P] 8-azido ATP.
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ABCC8 p.Lys719Arg 10204114:526:17
status: NEW[hide] Potassium channel openers require ATP to bind to a... EMBO J. 1998 Oct 1;17(19):5529-35. Schwanstecher M, Sieverding C, Dorschner H, Gross I, Aguilar-Bryan L, Schwanstecher C, Bryan J
Potassium channel openers require ATP to bind to and act through sulfonylurea receptors.
EMBO J. 1998 Oct 1;17(19):5529-35., [PMID:9755153]
Abstract [show]
KATP channels are composed of a small inwardly rectifying K+ channel subunit, either KIR6.1 or KIR6.2, plus a sulfonylurea receptor, SUR1 or SUR2 (A or B), which belong to the ATP-binding cassette superfamily. SUR1/KIR6.2 reconstitute the neuronal/pancreatic beta-cell channel, whereas SUR2A/KIR6.2 and SUR2B/KIR6.1 (or KIR6.2) are proposed to reconstitute the cardiac and the vascular-smooth-muscle-type KATP channels, respectively. We report that potassium channel openers (KCOs) bind to and act through SURs and that binding to SUR1, SUR2A and SUR2B requires ATP. Non-hydrolysable ATP-analogues do not support binding, and Mg2+ or Mn2+ are required. Point mutations in the Walker A motifs or linker regions of both nucleotide-binding folds (NBFs) abolish or weaken [3H]P1075 binding to SUR2B, rendering reconstituted SUR2B/KIR6.2 channels insensitive towards KCOs. The C-terminus of SUR affects KCO affinity with SUR2B approximately SUR1 > SUR2A. KCOs belonging to different structural classes inhibited specific [3H]P1075 binding to SUR2B in a monophasic manner, with the exception of minoxidil sulfate, which induced a biphasic displacement. The affinities of KCO binding to SUR2B were 3.5-8-fold higher than their potencies for activation of SUR2B/KIR6.2 channels. The results establish that SURs are the KCO receptors of KATP channels and suggest that KCO binding requires a conformational change induced by ATP hydrolysis in both NBFs.
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No. Sentence Comment
114 However, by analogy with the results seen with SUR2B, substitution of a lysine for an arginine in either NBF of SUR1 (K719R and/or K1384R) eliminates diazoxide binding and induces a complete loss of activation of SUR1/KIR6.2 channels (results not shown).
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ABCC8 p.Lys719Arg 9755153:114:118
status: NEW[hide] A novel ABCC8 (SUR1)-dependent mechanism of metabo... J Biol Chem. 2008 Apr 4;283(14):8778-82. Epub 2008 Feb 15. Babenko AP
A novel ABCC8 (SUR1)-dependent mechanism of metabolism-excitation uncoupling.
J Biol Chem. 2008 Apr 4;283(14):8778-82. Epub 2008 Feb 15., [PMID:18281290]
Abstract [show]
ATP/ADP-sensing (sulfonylurea receptor (SUR)/K(IR)6)(4) K(ATP) channels regulate the excitability of our insulin secreting and other vital cells via the differential MgATP/ADP-dependent stimulatory actions of their tissue-specific ATP-binding cassette regulatory subunits (sulfonylurea receptors), which counterbalance the nearly constant inhibitory action of ATP on the K(+) inwardly rectifying pore. Mutations in SUR1 that abolish its stimulation have been found in infants persistently releasing insulin. Activating mutations in SUR1 have been shown to cause neonatal diabetes. Here, analyses of K(IR)6.2-based channels with diabetogenic receptors reveal that MgATP-dependent hyper-stimulation of mutant SUR can compromise the ability of K(ATP) channels to function as metabolic sensors. I demonstrate that the channel hyperactivity rises exponentially with the number of hyperstimulating subunits, so small subpopulations of channels with more than two mutant SUR can dominate hyperpolarizing currents in heterozygous patients. I uncovered an attenuated tolbutamide inhibition of the hyperstimulated mutant, which is normally sensitive to the drug under non-stimulatory conditions. These findings show the key role of SUR in sensing the metabolic index in humans and urge others to (re)test mutant SUR/K(IR)6 channels from probands in physiologic MgATP.
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80 Second, K719R plus K1384R in the Walker A motifs eliminated the differences between the two channel activities on-cell and in 1 mM MgATP; the fractions of the Pomax were 0.003 Ϯ 0.0012 and 0.0034 Ϯ 0.0018 versus 0.0025 Ϯ 0.001 and 0.0028 Ϯ 0.0011 for NDSUR1K719RϩK1384R versus SUR1K719RϩK1384R channel, respectively (n ϭ 3 for each).
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ABCC8 p.Lys719Arg 18281290:80:8
status: NEW[hide] Subunit stoichiometry of the pancreatic beta-cell ... FEBS Lett. 1997 Jun 9;409(2):232-6. Inagaki N, Gonoi T, Seino S
Subunit stoichiometry of the pancreatic beta-cell ATP-sensitive K+ channel.
FEBS Lett. 1997 Jun 9;409(2):232-6., [PMID:9202152]
Abstract [show]
We have investigated the subunit stoichiometry of the pancreatic beta-cell ATP-sensitive K+ (KATP) channel (SUR1/Kir6.2 channel) by constructing cDNA encoding a single polypeptide (beta alpha polypeptide) consisting of a SUR1 (beta) subunit and a Kir6.2 (alpha) subunit. 86Rb+ efflux and single-channel properties of COS1 cells expressing beta alpha polypeptides were similar to those of COS1 cells coexpressing alpha monomers and beta monomers. Coexpression of beta alpha polypeptides with alpha monomers inhibited the K+ currents, while coexpression with beta monomers did not. We then constructed another single polypeptide (beta alpha2) consisting of a beta subunit and a dimeric repeat of the alpha subunit. 86Rb+ efflux from COS1 cells expressing beta alpha2 polypeptides was small, but was restored by supplementation with beta monomers. These results indicate that the activity of K(ATP) channels is optimized when the alpha and beta subunits are coexpressed with a molar ratio of 1:1. Since inward rectifier K+ channels are thought to function as homo- or hetero-tetramers, this suggests that the K(ATP) channel functions as a multimeric protein, most likely a hetero-octamer composed of a tetramer of the Kir6.2 subunit and a tetramer of the SUR1 subunit.
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32 The K719R mutation in the Walker A motif [4,16] in the first nucleotide-binding fold (NBF)-l of SURI and the G132S mutation in the H5 region of Kir6.2 were introduced using 21-mer oligonucleotides according to the manufacturer's instructions (in vitro mutagenesis system, Promega).
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ABCC8 p.Lys719Arg 9202152:32:4
status: NEW129 Mutß, the mutant ß of which amino acid residue lysine-719 was mutated to arginine.
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ABCC8 p.Lys719Arg 9202152:129:57
status: NEW[hide] ATP-sensitive potassium channels: a model of heter... Annu Rev Physiol. 1999;61:337-62. Seino S
ATP-sensitive potassium channels: a model of heteromultimeric potassium channel/receptor assemblies.
Annu Rev Physiol. 1999;61:337-62., [PMID:10099692]
Abstract [show]
ATP-sensitive K+ channels (KATP channels) play important roles in many cellular functions by coupling cell metabolism to electrical activity. By cloning members of the novel inwardly rectifying K+ channel subfamily Kir6.0 (Kir6.1 and Kir6.2) and the receptors for sulfonylureas (SUR1 and SUR2), researchers have clarified the molecular structure of KATP channels. KATP channels comprise two subunits: a Kir6.0 subfamily subunit, which is a member of the inwardly rectifying K+ channel family; and a SUR subunit, which is a member of the ATP-binding cassette (ABC) protein superfamily. KATP channels are the first example of a heteromultimeric complex assembled with a K+ channel and a receptor that are structurally unrelated to each other. Since 1995, molecular biological and molecular genetic studies of KATP channels have provided insights into the structure-function relationships, molecular regulation, and pathophysiological roles of KATP channels.
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No. Sentence Comment
230 Both mutations of the lysine in the Walker A motif (K719R, K719M) and a mutation of the aspartic acid in the Walker B motif (D854N) of SUR1 impair Mg2+ -independent high-affinity ATP binding (124).
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ABCC8 p.Lys719Arg 10099692:230:52
status: NEW[hide] The structure and function of the ATP-sensitive K+... J Mol Endocrinol. 1999 Apr;22(2):113-23. Miki T, Nagashima K, Seino S
The structure and function of the ATP-sensitive K+ channel in insulin-secreting pancreatic beta-cells.
J Mol Endocrinol. 1999 Apr;22(2):113-23., [PMID:10194514]
Abstract [show]
ATP-sensitive K+ channels (KATP channels) play important roles in many cellular functions by coupling cell metabolism to electrical activity. The KATP channels in pancreatic beta-cells are thought to be critical in the regulation of glucose-induced and sulfonylurea-induced insulin secretion. Until recently, however, the molecular structure of the KATP channel was not known. Cloning members of the novel inwardly rectifying K+ channel subfamily Kir6.0 (Kir6.1 and Kir6.2) and the sulfonylurea receptors (SUR1 and SUR2) has clarified the molecular structure of KATP channels. The pancreatic beta-cell KATP channel comprises two subunits: a Kir6.2 subunit and an SUR1 subunit. Molecular biological and molecular genetic studies have provided insights into the physiological and pathophysiological roles of the pancreatic beta-cell KATP channel in insulin secretion.
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No. Sentence Comment
97 Mutations of Walker A (K719R and K719M) in NBF-1 and Walker B (D854N) in NBF-1 of SUR1 severely impair Mg2+ -independent high-affinity ATP binding.
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ABCC8 p.Lys719Arg 10194514:97:23
status: NEW[hide] MgADP antagonism to Mg2+-independent ATP binding o... J Biol Chem. 1997 Sep 12;272(37):22983-6. Ueda K, Inagaki N, Seino S
MgADP antagonism to Mg2+-independent ATP binding of the sulfonylurea receptor SUR1.
J Biol Chem. 1997 Sep 12;272(37):22983-6., [PMID:9287292]
Abstract [show]
Pancreatic beta-cell ATP-sensitive potassium (KATP) channels play an important role in the regulation of glucose-induced insulin secretion. The beta-cell KATP channel comprises two subunits, the sulfonylurea receptor SUR1, a member of the ATP-binding cassette (ABC) superfamily, and Kir6.2, a member of the inward rectifier K+ channel family. The activity of the KATP channel is under complex regulation by the intracellular ATP and ADP. To understand the roles of the two nucleotide-binding folds (NBFs) of SUR1 in the regulation of KATP channel activity, we introduced point mutations into the core consensus sequence of the Walker A or B motif of each NBF of SUR1 and characterized ATP binding and ADP or MgADP antagonism to it. SUR1 was efficiently photolabeled with 8-azido-[alpha-32P]ATP and 8-azido-[gamma-32P]ATP in the presence or absence of Mg2+ or vanadate. NBF1 mutations impaired ATP binding, but NBF2 mutations did not. MgADP strongly antagonized ATP binding, and the NBF2 mutation reduced MgADP antagonism. These results show that SUR1, unlike other ABC proteins, strongly binds ATP at NBF1 even in the absence of Mg2+ and that MgADP, through binding at NBF2, antagonizes the Mg2+-independent high affinity ATP binding at NBF1.
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No. Sentence Comment
61 Substitutions of the conserved lysine in Walker A, K719R and K719M (lanes 2 and 3), or the aspartate in Walker B, D854N (lane 4), abolished the binding of 5 M 8-azido-[␣-32 P]ATP, although substitutions at equivalent sites in NBF2, K1385R, K1385M, or D1506N (lanes 5, 6, and 7) did not affect it. SUR1 with mutations in NBF1 binds ATP only slightly even when incubated with 40 M 8-azido-[␣-32 P]ATP.
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ABCC8 p.Lys719Arg 9287292:61:51
status: NEW96 However, we have observed that while K719M and K719R mutants severely impair functional expression of KATP channels, K1385M and K1385R mutants do not.2 Although whether or not SUR1 has ATP hydrolysis activity is unknown, ATP binding to NBF1 of SUR1 might be important in maintaining KATP channels in the operative state.
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ABCC8 p.Lys719Arg 9287292:96:47
status: NEW103 Lane 1, wild-type SUR1; lane 2, K719R; lane 3, K719M; lane 4, D854N; lane 5, K1385R; lane 6, K1385M; lane 7, D1506N.
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ABCC8 p.Lys719Arg 9287292:103:32
status: NEW