ABCB1 p.Val71Arg
| Predicted by SNAP2: | A: N (57%), C: N (78%), D: D (66%), E: D (63%), F: N (87%), G: D (59%), H: D (59%), I: N (93%), K: D (66%), L: N (87%), M: N (61%), N: D (63%), P: D (71%), Q: D (53%), R: D (66%), S: D (53%), T: N (57%), W: D (71%), Y: D (63%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: N, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: D, T: D, W: D, Y: D, |
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[hide] Arginines in the first transmembrane segment promo... J Biol Chem. 2008 Sep 5;283(36):24860-70. Epub 2008 Jul 2. Loo TW, Bartlett MC, Clarke DM
Arginines in the first transmembrane segment promote maturation of a P-glycoprotein processing mutant by hydrogen bond interactions with tyrosines in transmembrane segment 11.
J Biol Chem. 2008 Sep 5;283(36):24860-70. Epub 2008 Jul 2., 2008-09-05 [PMID:18596043]
Abstract [show]
A key goal is to correct defective folding of mutant ATP binding cassette (ABC) transporters, as they cause diseases such as cystic fibrosis. P-glycoprotein (ABCB1) is a useful model system because introduction of an arginine at position 65 of the first transmembrane (TM) segment could repair folding defects. To determine the mechanism of arginine rescue, we first tested the effects of introducing arginines at other positions in TM1 (residues 52-72) of a P-glycoprotein processing mutant (G251V) that is defective in folding and trafficking to the cell surface (20% maturation efficiency). We found that arginines introduced into one face of the TM1 helix (positions 52, 55, 56, 59, 60, 62, 63, 66, and 67) inhibited maturation, whereas arginines on the opposite face of the helix promoted (positions 64, 65, 68, and 71) or had little effect (positions 61, and 69) on maturation. Arginines at positions 61, 64, 65, and 68 appeared to lie close to the drug binding sites as they reduced the apparent affinity for drug substrates such as vinblastine and verapamil. Therefore, arginines that promoted maturation may face an aqueous drug translocation pathway, whereas those that inhibited maturation may face the lipid bilayer. The highest maturation efficiencies (60-85%) were observed with the Arg-65 and Arg-68 mutants. Mutations that removed hydrogen bond acceptors (Y950F/Y950A or Y953F/Y953A) in TM11 predicted to lie close to Arg-65 or Arg-68 inhibited maturation but did not affect maturation of the G251V parent. Therefore, arginine may rescue defective folding by promoting packing of the TM segments through hydrogen bond interactions.
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No. Sentence Comment
55 For disulfide cross-linking analysis, the cDNA of mutant L339C(TM6)/F728C(TM7) (16) was modified to also encode the G64R, M68R, or V71R mutations.
X
ABCB1 p.Val71Arg 18596043:55:131
status: NEW104 Mutants G64R and V71R showed maturation efficiencies of FIGURE 1.
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ABCB1 p.Val71Arg 18596043:104:17
status: NEW156 Because the G64R and V71R changes also promoted maturation of the G251V processing mutant (Fig. 2), we also introduced these mutations into the L339C(TM6)/F728C(TM7) mutant.
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ABCB1 p.Val71Arg 18596043:156:21
status: NEW165 TABLE 1 Effects of drug substrates on the maturation of TM1 arginine mutants containing the G251V mutation Mutation (G251V ؉) No drug Cyclosporin A Verapamil Vinblastine Rhodamine None - 111a,c 111 111 11 V52R -a,b 111 111 111 11 V53R 2 - - - - G64R 2 - - - - T55R 2 - - - - L56R 2 - - - - A57R 2 - - - - A58R 2 - - - - I59R 2 - - - - I60R 2 - - - - H61R - 111 1 1 1 G62R 2 - - - - A63R 2 - - - - G64R 1 111 1 1 11 L65R 11 111 11 11 11 P66R 2 1 - - - L67R - 111 111 111 11 M68R 111 111 111 111 111 M69R - 111 - 11 111 L70R - 111 111 111 11 V71R 1 111 111 111 11 F72R 2 1 1 1 1 a Change in the amount of mature (170 kDa) protein in the presence of drug substrate relative to that in the absence of drug substrate.
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ABCB1 p.Val71Arg 18596043:165:546
status: NEW173 Membranes were prepared from HEK 293 cells expressing mutants L339C(TM6)/F728C(TM7), G64R/ L339C(TM6)/F728C(TM7), M68R/ L339C(TM6)/F728C(TM7), and V71R/L339C(TM6)/F728C(TM7).
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ABCB1 p.Val71Arg 18596043:173:147
status: NEW181 The G64R/L339C(TM6)/ F728C(TM7) mutant also showed a large reduction in apparent affinity for vinblastine (Ͼ100-fold), whereas the V71R change had little effect.
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ABCB1 p.Val71Arg 18596043:181:137
status: NEW194 TABLE 2 Concentrations of drug substrates required to inhibit cross-linking by 50% Mutant Vinblastine Cyclosporin A Rhodamine B M M M L339C/F728C 0.5 Ϯ 0.2a 0.8 Ϯ 0.3 52 Ϯ 14 G64R/L339C/F728C 53 Ϯ 15b 1.5 Ϯ 0.4 61 Ϯ 10 M68R/L339C/F728C 266 Ϯ 62b 1.3 Ϯ 0.3 57 Ϯ 7 V71R/L339C/F728C 0.6 Ϯ 0.2 0.8 Ϯ 0.2 57 Ϯ 10 a Each value is the mean Ϯ S.D. (n ϭ 3-4 separate cross-linking experiments).
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ABCB1 p.Val71Arg 18596043:194:341
status: NEW278 Residue Val-71, however, appeared to lie outside the drug binding pocket since the V71R mutation did not affect P-gp-drug interactions (Table 3).
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ABCB1 p.Val71Arg 18596043:278:83
status: NEW298 Some mutations such as G64R, L65R, M68R, and V71R actually promoted maturation of the G251V mutant.
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ABCB1 p.Val71Arg 18596043:298:45
status: NEW