ABCMdb

ABCC8 p.Ile49Gly

Predicted by SNAP2:	A: N (66%), C: N (82%), D: D (59%), E: N (53%), F: N (78%), G: N (53%), H: N (57%), K: N (53%), L: N (97%), M: N (93%), N: N (53%), P: D (59%), Q: N (66%), R: N (57%), S: N (87%), T: N (78%), V: N (97%), W: N (61%), Y: N (66%),
Predicted by PROVEAN:	A: N, C: N, D: D, E: D, F: N, G: D, H: D, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: D, T: N, V: N, W: D, Y: D,

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[hide] Involvement of the N-terminus of Kir6.2 in the inh... J Physiol. 1999 Jan 1;514 ( Pt 1):19-25. Proks P, Gribble FM, Adhikari R, Tucker SJ, Ashcroft FM
Involvement of the N-terminus of Kir6.2 in the inhibition of the KATP channel by ATP.
J Physiol. 1999 Jan 1;514 ( Pt 1):19-25., [PMID:9831713]

Abstract [show]
1. ATP-sensitive potassium (KATP) channels are composed of pore-forming Kir6.2 and regulatory SUR subunits. A truncated isoform of Kir6.2, Kir6.2DeltaC26, expresses ATP-sensitive channels in the absence of SUR1, suggesting the ATP-inhibitory site lies on the Kir6. 2 subunit. 2. We examined the effect on the channel ATP sensitivity of mutating the arginine residue at position 50 (R50) in the N-terminus of Kir6.2, by recording macroscopic currents in membrane patches excised from Xenopus oocytes expressing wild-type or mutant Kir6.2DeltaC26. 3. Substitution of R50 by serine, alanine or glycine reduced the Ki for ATP inhibition from 117 microM to 800 microM, 1.1 mM and 3.8 mM, respectively. The single-channel conductance and kinetics were unaffected by any of these mutations. Mutation to glutamate, lysine, asparagine, glutamine or leucine had a smaller effect (Ki, approximately 300-400 microM). The results indicate that the side chain of the arginine residue at position 50 is unlikely to contribute directly to the binding site for ATP, and suggest it may affect ATP inhibition by allosteric interactions. 4. Mutation of the isoleucine residue at position 49 to glycine (I49G) reduced the channel ATP sensitivity, while the mutation of the glutamate residue at position 51 to glycine (E51G) did not. 5. When a mutation in the N-terminus of Kir6.2DeltaC26 that alters ATP sensitivity (R50S; Ki, 800 microM) was combined with one in the C-terminus (E179Q; Ki, 300 microM), the Ki for the apparent ATP sensitivity was increased to 2.8 mM. The Hill coefficient was also increased. This suggests that the N- and C-termini of Kir6.2 may co-operate to influence channel closure by ATP.

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No. Sentence Comment
18 Mutation of the isoleucine residue at position 49 to glycine (I49G) reduced the channel ATP sensitivity, while the mutation of the glutamate residue at position 51 to glycine (E51G) did not. Login to comment
103 However when the isoleucine at position 49 was changed to glycine, ATP produced significantly less inhibition (I49G; Figs 3 and 5). Login to comment
106 Single-channel currents for wild-type and mutant Kir6.2ÄC26 channels Single-channel currents recorded at -60 mV from an inside-out patch excised from an oocyte injected with mRNA encoding wtKir6.2ÄC26 or Kir6.2ÄC26-I49G, in the absence and presence of ATP as indicated. Login to comment
109 Comparison of wild-type and mutant Kir6.2ÄC26 single-channel kinetics ------------------------------------------------------------ Clone Pï ôï ôC1 ôC2 %Cµ Burst duration Openings (n = 3) (ms) (ms) (ms) (ms) per burst ------------------------------------------------------------ Kir6.2ÄC26 0·11 ± 0·03 0·79 ± 0·06 0·31 ± 0·03 12·6 ± 2·9 41 ± 8 2·4 ± 0·6 2·4 ± 0·3 Kir6.2ÄC26-R50G 0·14 ± 0·07 0·99 ± 0·09 0·32 ± 0·01 9·1 ± 3·1 36 ± 3 2·6 ± 0·5 2·1 ± 0·4 Kir6.2ÄC26-R50A 0·09 ± 0·02 0·71 ± 0·04 0·29 ± 0·01 17·1 ± 4·7 44 ± 7 2·8 ± 0·6 2·6 ± 0·4 Kir6.2ÄC26-R50SÏE179Q 0·08 ± 0·02 0·75 ± 0·0 0·28 ± 0·01 9·4 ± 1·9 50 ± 2 2·7 ± 0·3 2·8 ± 0·3 Kir6.2ÄC26-I49G 0·13 ± 0·04 0·85 ± 0·07 0·29 ± 0·03 7·3 ± 1·8 32 ± 4 2·9 ± 0·2 2·7 ± 0·2 ------------------------------------------------------------ Kinetic parameters were measured at -60 mV, as described in Trapp et al. (1978). Login to comment
115 The reduced ATP sensitivity of the I49G mutant channel was not associated with a change in the single-channel kinetics (Fig. 5 and Table 2), suggesting that this mutation impairs either ATP binding or the mechanism by which binding is linked to channel closure. Login to comment