ABCC7 p.Gln552Ala
| ClinVar: |
c.1654C>T
,
p.Gln552*
D
, Pathogenic
|
| CF databases: |
c.1654C>T
,
p.Gln552*
D
, CF-causing
c.1654C>A , p.Gln552Lys (CFTR1) D , The mutation Q552K was detected by DGGE and direct sequencing in a patient from Brazil (Afro-American origin), he is homozygous for this mutation, with PI and mild lung involvement. |
| Predicted by SNAP2: | A: D (75%), C: D (71%), D: D (85%), E: D (71%), F: D (85%), G: D (80%), H: D (75%), I: D (85%), K: D (85%), L: D (85%), M: D (75%), N: D (75%), P: D (91%), R: D (85%), S: D (75%), T: D (80%), V: D (75%), W: D (85%), Y: D (80%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] On the mechanism of MgATP-dependent gating of CFTR... J Gen Physiol. 2003 Jan;121(1):17-36. Vergani P, Nairn AC, Gadsby DC
On the mechanism of MgATP-dependent gating of CFTR Cl- channels.
J Gen Physiol. 2003 Jan;121(1):17-36., [PMID:12508051]
Abstract [show]
CFTR, the product of the gene mutated in cystic fibrosis, is an ATPase that functions as a Cl(-) channel in which bursts of openings separate relatively long interburst closed times (tauib). Channel gating is controlled by phosphorylation and MgATP, but the underlying molecular mechanisms remain controversial. To investigate them, we expressed CFTR channels in Xenopus oocytes and examined, in excised patches, how gating kinetics of phosphorylated channels were affected by changes in [MgATP], by alterations in the chemical structure of the activating nucleotide, and by mutations expected to impair nucleotide hydrolysis and/or diminish nucleotide binding affinity. The rate of opening to a burst (1/tauib) was a saturable function of [MgATP], but apparent affinity was reduced by mutations in either of CFTR's nucleotide binding domains (NBDs): K464A in NBD1, and K1250A or D1370N in NBD2. Burst duration of neither wild-type nor mutant channels was much influenced by [MgATP]. Poorly hydrolyzable nucleotide analogs, MgAMPPNP, MgAMPPCP, and MgATPgammaS, could open CFTR channels, but only to a maximal rate of opening approximately 20-fold lower than attained by MgATP acting on the same channels. NBD2 catalytic site mutations K1250A, D1370N, and E1371S were found to prolong open bursts. Corresponding NBD1 mutations did not affect timing of burst termination in normal, hydrolytic conditions. However, when hydrolysis at NBD2 was impaired, the NBD1 mutation K464A shortened the prolonged open bursts. In light of recent biochemical and structural data, the results suggest that: nucleotide binding to both NBDs precedes channel opening; at saturating nucleotide concentrations the rate of opening to a burst is influenced by the structure of the phosphate chain of the activating nucleotide; normal, rapid exit from bursts occurs after hydrolysis of the nucleotide at NBD2, without requiring a further nucleotide binding step; if hydrolysis at NBD2 is prevented, exit from bursts occurs through a slower pathway, the rate of which is modulated by the structure of the NBD1 catalytic site and its bound nucleotide. Based on these and other results, we propose a mechanism linking hydrolytic and gating cycles via ATP-driven dimerization of CFTR's NBDs.
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No. Sentence Comment
34 Thus, the K1250A mutation dramatically prolonged burst duration, suggesting that hydrolysis at NBD2 might be coupled to burst termination (Carson et al., 1995; Gunderson and Kopito, 1995), whereas the NBD1 mutations K464A, Q552A, and Q552H somewhat slowed channel opening to a burst, suggesting that NBD1 might be a site of ATP interactions governing opening (Carson et al., 1995; Carson and Welsh 1995).
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ABCC7 p.Gln552Ala 12508051:34:223
status: NEW[hide] Structure and function of the CFTR chloride channe... Physiol Rev. 1999 Jan;79(1 Suppl):S23-45. Sheppard DN, Welsh MJ
Structure and function of the CFTR chloride channel.
Physiol Rev. 1999 Jan;79(1 Suppl):S23-45., [PMID:9922375]
Abstract [show]
Structure and Function of the CFTR Chloride Channel. Physiol. Rev. 79, Suppl.: S23-S45, 1999. - The cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ABC transporter family that forms a novel Cl- channel. It is located predominantly in the apical membrane of epithelia where it mediates transepithelial salt and liquid movement. Dysfunction of CFTR causes the genetic disease cystic fibrosis. The CFTR is composed of five domains: two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs), and a regulatory (R) domain. Here we review the structure and function of this unique channel, with a focus on how the various domains contribute to channel function. The MSDs form the channel pore, phosphorylation of the R domain determines channel activity, and ATP hydrolysis by the NBDs controls channel gating. Current knowledge of CFTR structure and function may help us understand better its mechanism of action, its role in electrolyte transport, its dysfunction in cystic fibrosis, and its relationship to other ABC transporters.
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No. Sentence Comment
375 This is consistent with the finding that in the absence predicted to decrease the rate of hydrolysis at NBD1, for example, K464A and Q552A, would thus increase the in-of ATP, the channel does not open.
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ABCC7 p.Gln552Ala 9922375:375:133
status: NEW[hide] Structural and functional similarities between the... Biophys J. 1995 Dec;69(6):2443-8. Carson MR, Welsh MJ
Structural and functional similarities between the nucleotide-binding domains of CFTR and GTP-binding proteins.
Biophys J. 1995 Dec;69(6):2443-8., [PMID:8599650]
Abstract [show]
The opening and closing of the CFTR Cl- channel are regulated by ATP hydrolysis at its two nucleotide binding domains (NBDs). However, the mechanism and functional significance of ATP hydrolysis are unknown. Sequence similarity between the NBDs of CFTR and GTP-binding proteins suggested the NBDs might have a structure and perhaps a function like that of GTP-binding proteins. Based on this similarity, we predicted that the terminal residue of the LSGGQ motif in the NBDs of CFTR corresponds to a highly conserved glutamine residue in GTP-binding proteins that directly catalyzes the GTPase reaction. Mutations of this residue in NBD1 or NBD2, which were predicted to increase or decrease the rate of hydrolysis, altered the duration of channel closed and open times in a specific manner without altering ion conduction properties or ADP-dependent inhibition. These results suggest that the NBDs of CFTR, and consequently other ABC transporters, may have a structure and a function analogous to those of GTP-binding proteins. We conclude that the rates of ATP hydrolysis at NBD1 and at NBD2 determine the duration of the two states of the channel, closed and open, much as the rate of GTP hydrolysis by GTP-binding proteins determines the duration of their active state.
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No. Sentence Comment
27 To test these hypotheses we used the excised inside-out patch-clamp technique to study CFTR variants containing the Q552A, Q552H, H1350Q, and H1350A mutations.
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ABCC7 p.Gln552Ala 8599650:27:116
status: NEW72 That is, Q552A and Q552H decreased the rate at A. I I 40 80 120 V (mV) I (pA) 0.50- P0 FIGURE 2 Effect of Q552 and H1350 mutations on CFTR Cl- chan- nels.
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ABCC7 p.Gln552Ala 8599650:72:9
status: NEW77 Open circles, wild-type; open triangles, Q552A; open squares, Q552H; filled circles, H1350A; filled triangles, H1350Q.
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ABCC7 p.Gln552Ala 8599650:77:41
status: NEW90 Fig. 2 A shows 0.250- B. 2000- mean closed-time between 1000- bursts (ms) 0- C. mean burst duration (ms) wild-type T T k" IffilI -.. wild- Q552A 0552H H1350Q H1350A type 3001 wilt'- type FIGURE 3 Effect of mutation of Q552 and H1350 on single channel activity.
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ABCC7 p.Gln552Ala 8599650:90:139
status: NEW