ABCB1 p.Thr199Arg
| Predicted by SNAP2: | A: D (59%), C: D (66%), D: D (80%), E: D (85%), F: D (85%), G: D (53%), H: D (71%), I: D (63%), K: D (91%), L: D (66%), M: N (66%), N: D (75%), P: D (91%), Q: D (66%), R: D (71%), S: N (72%), V: D (80%), W: D (85%), Y: D (75%), |
| 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, Q: D, R: D, S: N, V: D, W: D, Y: D, |
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[hide] Suppressor mutations in the transmembrane segments... J Biol Chem. 2007 Nov 2;282(44):32043-52. Epub 2007 Sep 11. Loo TW, Bartlett MC, Clarke DM
Suppressor mutations in the transmembrane segments of P-glycoprotein promote maturation of processing mutants and disrupt a subset of drug-binding sites.
J Biol Chem. 2007 Nov 2;282(44):32043-52. Epub 2007 Sep 11., 2007-11-02 [PMID:17848563]
Abstract [show]
Defective folding of cystic fibrosis transmembrane conductance regulator protein missing Phe508 (DeltaF508) is the major cause of cystic fibrosis. The folding defect in DeltaF508 cystic fibrosis transmembrane conductance regulator might be correctable because misfolding of a P-glycoprotein (P-gp; ABCB1) mutant lacking the equivalent residue (DeltaY490) could be corrected with drug substrates or by introduction of an arginine residue into transmembrane (TM) segments 5 (I306R) or 6 (F343R). Possible mechanisms of arginine rescue were that they mimicked some of the effects of drug substrate interactions with P-gp or that they affected global folding such that all drug substrate/modulator interactions with P-gp were altered. To distinguish between these mechanisms, we tested whether arginines introduced into other TMs predicted to line the drug-binding pocket (TM1 or TM3) would affect folding. It was found that mutation of L65R(TM1) or T199R(TM3) promoted maturation of processing mutants. We then tested whether arginine suppressor mutations had local or global effects on P-gp interactions with drug substrates and modulators. The L65R(TM1), T199R(TM3), I306R(TM5), or F343R(TM6) mutations were introduced into the P-gp mutant L339C(TM6)/F728C(TM7), and thiol cross-linking was carried out in the presence of various concentrations of vinblastine, cyclosporin A, or rhodamine B. The presence of arginine residues reduced the apparent affinity of P-gp for vinblastine (L65R, T199R, and I306R), cyclosporin (I306R and F343R), or rhodamine B (F343R) by 4-60-fold. These results show that the arginine mutations affect a subset of drug-binding sites and suggest that they rescue processing mutants by mimicking drug substrate interactions with P-gp.
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No. Sentence Comment
7 The presence of arginine residues reduced the apparent affinity of P-gp for vinblastine (L65R, T199R, and I306R), cyclosporin (I306R and F343R), or rhodamine B (F343R) by 4-60-fold.
X
ABCB1 p.Thr199Arg 17848563:7:95
status: NEW69 For disulfide cross-linking analysis, the cDNA of mutant L339C(TM6)/ F728C(TM7) (34) was modified to also encode the L65R, T199R, I306R, or F343R mutations.
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ABCB1 p.Thr199Arg 17848563:69:123
status: NEW164 Effect of L65R and T199R Mutations on Maturation of a P-gp Processing Mutant-We then tested whether arginines introduced into TM1 (Leu65 ) (27) or TM3 (Thr199 ) promoted maturation of a P-gp processing mutant.
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ABCB1 p.Thr199Arg 17848563:164:19
status: NEW271 It is possible, however, that residue 199 lies some distance away from the actual rhodamine B binding site because the T199R mutation did not reduce the apparent affinity for rhodamine B in the cross-linking protection assay (Table 1).
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ABCB1 p.Thr199Arg 17848563:271:119
status: NEW273 The residue at position 199 in TM3, however, does appear to lie close to the vinblastine-binding site because the T199R mutation reduced the apparent affinity for vinblastine by 6.4-fold (Table 1).
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ABCB1 p.Thr199Arg 17848563:273:114
status: NEW