ABCB1 p.Thr55Arg
| Predicted by SNAP2: | A: N (66%), C: N (82%), D: D (71%), E: D (75%), F: D (66%), G: N (66%), H: D (63%), I: N (72%), K: D (80%), L: N (66%), M: D (63%), N: N (61%), P: D (66%), Q: D (75%), R: D (80%), S: N (87%), V: N (66%), W: D (75%), 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] 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
142 Therefore, mutants showing reduced (T55R/G251V) or similar maturation efficiencies (H61R/G251V, M69R/G251V) to the G251V parent were expressed in the presence of 5 M cyclosporin A, 30 M verapamil, 5 M vinblastine, or 30 M rhodamine B.
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ABCB1 p.Thr55Arg 18596043:142:36
status: NEW144 By contrast, a mutant where the introduced arginine inhibited maturation of G251V (mutant T55R) could not be rescued with any of the drug substrates (Fig. 5).
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ABCB1 p.Thr55Arg 18596043:144:90
status: NEW151 By contrast, 12 of the mutants (V53R, G54R, T55R, L56R, A57R, A58R, I59R, I60R, G62R, A63R, P66R, and F72R) showed little or no rescue in the presence of drug substrates.
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ABCB1 p.Thr55Arg 18596043:151:44
status: NEW163 HEK 293 cells expressing mutants G251V, T55R/G251V, H61R/G251V, or M69R/G251V were treated with no drug (None), 5 M cyclosporin A (Cyclo), 30 M verapamil (Ver), 5 M vinblastine (Vin), or 30 M rhodamine B (Rhod) for 24 h. Whole cell extracts were then subjected to immunoblot analysis.
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ABCB1 p.Thr55Arg 18596043:163:40
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.Thr55Arg 18596043:165:266
status: NEW[hide] Mutation of Glu521 or Glu535 in cytoplasmic loop 5... J Biol Chem. 2012 Mar 2;287(10):7543-55. Epub 2012 Jan 9. Iram SH, Cole SP
Mutation of Glu521 or Glu535 in cytoplasmic loop 5 causes differential misfolding in multiple domains of multidrug and organic anion transporter MRP1 (ABCC1).
J Biol Chem. 2012 Mar 2;287(10):7543-55. Epub 2012 Jan 9., [PMID:22232552]
Abstract [show]
The polytopic 5-domain multidrug resistance protein 1 (MRP1/ABCC1) extrudes a variety of drugs and organic anions across the plasma membrane. Four charged residues in the fifth cytoplasmic loop (CL5) connecting transmembrane helix 9 (TM9) to TM10 are critical for stable expression of MRP1 at the plasma membrane. Thus Ala substitution of Lys(513), Lys(516), Glu(521), and Glu(535) all cause misfolding of MRP1 and target the protein for proteasome-mediated degradation. Of four chemical chaperones tested, 4-phenylbutyric acid (4-PBA) was the most effective at restoring expression of MRP1 mutants K513A, K516A, E521A, and E535A. However, although 4-PBA treatment of K513A resulted in wild-type protein levels (and activity), the same treatment had little or no effect on the expression of K516A. On the other hand, 4-PBA treatment allowed both E521A and E535A to exit the endoplasmic reticulum and be stably expressed at the plasma membrane. However, the 4-PBA-rescued E535A mutant exhibited decreased transport activity associated with reduced substrate affinity and conformational changes in both halves of the transporter. By contrast, E521A exhibited reduced transport activity associated with alterations in the mutant interactions with ATP as well as a distinct conformational change in the COOH-proximal half of MRP1. These findings illustrate the critical and complex role of CL5 for stable expression of MRP1 at the plasma membrane and more specifically show the differential importance of Glu(521) and Glu(535) in interdomain interactions required for proper folding and assembly of MRP1 into a fully transport competent native structure.
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No. Sentence Comment
261 Thus, the P-glycoprotein processing mutant G251V/T55R is not rescued by any drug substrates, whereas another mutant G251V/H61R can be rescued by only a single substrate (cyclosporine A) (39).
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ABCB1 p.Thr55Arg 22232552:261:49
status: NEW