ABCB1 p.Phe72Arg
| Predicted by SNAP2: | A: D (59%), C: N (61%), D: D (85%), E: D (75%), G: D (75%), H: D (75%), I: D (53%), K: D (85%), L: N (66%), M: N (61%), N: D (80%), P: D (85%), Q: D (63%), R: D (80%), S: D (66%), T: D (66%), V: D (59%), W: D (66%), Y: N (78%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: N, |
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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
117 Introduction of arginines at other positions at the extracellular end of TM1 had little effect (10-20% mature P-gp in mutants L67R, M69R, and L70R) or reduced the level of mature product to less than 10% of total P-gp (mutants P66R and F72R).
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ABCB1 p.Phe72Arg 18596043:117:236
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.Phe72Arg 18596043:151:102
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.Phe72Arg 18596043:165:568
status: NEW[hide] Mapping the Binding Site of the Inhibitor Tariquid... J Biol Chem. 2015 Dec 4;290(49):29389-401. doi: 10.1074/jbc.M115.695171. Epub 2015 Oct 26. Loo TW, Clarke DM
Mapping the Binding Site of the Inhibitor Tariquidar That Stabilizes the First Transmembrane Domain of P-glycoprotein.
J Biol Chem. 2015 Dec 4;290(49):29389-401. doi: 10.1074/jbc.M115.695171. Epub 2015 Oct 26., [PMID:26507655]
Abstract [show]
ABC (ATP-binding cassette) transporters are clinically important because drug pumps like P-glycoprotein (P-gp, ABCB1) confer multidrug resistance and mutant ABC proteins are responsible for many protein-folding diseases such as cystic fibrosis. Identification of the tariquidar-binding site has been the subject of intensive molecular modeling studies because it is the most potent inhibitor and corrector of P-gp. Tariquidar is a unique P-gp inhibitor because it locks the pump in a conformation that blocks drug efflux but activates ATPase activity. In silico docking studies have identified several potential tariquidar-binding sites. Here, we show through cross-linking studies that tariquidar most likely binds to sites within the transmembrane (TM) segments located in one wing or at the interface between the two wings (12 TM segments form 2 divergent wings). We then introduced arginine residues at all positions in the 12 TM segments (223 mutants) of P-gp. The rationale was that a charged residue in the drug-binding pocket would disrupt hydrophobic interaction with tariquidar and inhibit its ability to rescue processing mutants or stimulate ATPase activity. Arginines introduced at 30 positions significantly inhibited tariquidar rescue of a processing mutant and activation of ATPase activity. The results suggest that tariquidar binds to a site within the drug-binding pocket at the interface between the TM segments of both structural wings. Tariquidar differed from other drug substrates, however, as it stabilized the first TM domain. Stabilization of the first TM domain appears to be a key mechanism for high efficiency rescue of ABC processing mutants that cause disease.
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No. Sentence Comment
175 In the N-terminal TMD1 domain, the largest number of arginine mutations predicted to line the drug-binding pocket that inhibited tariquidar rescue were located in TM1 (H61R, G64R, L65R, M68R, M69R, and F72R) and TM5 (F303R, I306R, Y307R, S309R, and Y310R) (Fig. 4, A and E).
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ABCB1 p.Phe72Arg 26507655:175:202
status: NEW194 The other 12 mutants in TM1 (F72R), TM5 (Y307R and Y310R), TM6 (F336R and F343R), TM7 (F732R), TM10 (V865R), TM11 (M949R, Y950R, S952R, and Y953R), and TM12 (L975R and F978R) were not rescued by cyclosporine A (Fig. 7).
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ABCB1 p.Phe72Arg 26507655:194:29
status: NEW212 Seventeen of the 30 G251V/arginine mutants (M68R, M69R, and F72R in TM1; I306R, Y307R, S309R, and Y310R in TM5; F336R in TM6; F728R and F732R in TM7; I868R and G872R in TM10; F942R, T945R, M949R, and S952R in TM11; and V982R in TM12) that could not be rescued with tariquidar showed little or no stimulation of ATPase activity with tariquidar (Fig. 8A).
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ABCB1 p.Phe72Arg 26507655:212:60
status: NEW