ABCC1 p.Trp445Tyr
| Predicted by SNAP2: | A: D (85%), C: D (80%), D: D (95%), E: D (91%), F: D (75%), G: D (91%), H: D (91%), I: D (80%), K: D (95%), L: D (85%), M: D (80%), N: D (91%), P: D (95%), Q: D (91%), R: D (91%), S: D (91%), T: D (91%), V: D (80%), Y: D (85%), |
| 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: D, T: D, V: D, Y: D, |
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[hide] Multiple membrane-associated tryptophan residues c... J Biol Chem. 2002 Dec 20;277(51):49495-503. Epub 2002 Oct 17. Koike K, Oleschuk CJ, Haimeur A, Olsen SL, Deeley RG, Cole SP
Multiple membrane-associated tryptophan residues contribute to the transport activity and substrate specificity of the human multidrug resistance protein, MRP1.
J Biol Chem. 2002 Dec 20;277(51):49495-503. Epub 2002 Oct 17., 2002-12-20 [PMID:12388549]
Abstract [show]
The multidrug resistance protein, MRP1, is a clinically important ATP-binding cassette transporter in which the three membrane-spanning domains (MSDs), which contain up to 17 transmembrane (TM) helices, and two nucleotide binding domains (NBDs) are configured MSD1-MSD2-NBD1-MSD3-NBD2. In tumor cells, MRP1 confers resistance to a broad spectrum of drugs, but in normal cells, it functions as a primary active transporter of organic anions such as leukotriene C(4) and 17beta-estradiol 17beta-(D-glucuronide). We have previously shown that mutation of TM17-Trp(1246) eliminates 17beta-estradiol 17beta-(D-glucuronide) transport and drug resistance conferred by MRP1 while leaving leukotriene C(4) transport intact. By mutating the 11 remaining Trp residues that are in predicted TM segments of MRP1, we have now determined that five of them are also major determinants of MRP1 function. Ala substitution of three of these residues, Trp(445) (TM8), Trp(553) (TM10), and Trp(1198) (TM16), eliminated or substantially reduced transport levels of five organic anion substrates of MRP1. In contrast, Ala substitutions of Trp(361) (TM7) and Trp(459) (TM9) caused a more moderate and substrate-selective reduction in MRP1 function. More conservative substitutions (Tyr and Phe) of the Trp(445), Trp(553), and Trp(1198) mutants resulted in substrate selective retention of transport in some cases (Trp(445) and Trp(1198)) but not others (Trp(553)). Our findings suggest that the bulky polar aromatic indole side chain of each of these five Trp residues contributes significantly to the transport activity and substrate specificity of MRP1.
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No. Sentence Comment
48 Tryptophan substitutions were generated in the pGEM-3Z and pBluescriptSK(ϩ) plasmids above according to the manufacturer`s instructions with the following mutagenic primers (substituted nucleotides are underlined): MSD1 Trp mutants W40A (5Ј-G GTC CTC GTG GCC GTG CCT TG-3Ј, W47A (5Ј-GT TTT TAC CTC GCC GCC TGT TTC CCC-3Ј), W82A (5Ј-C TTG GGA TTT TTG CTG GCG ATC GTC TGC TGG GC-3Ј), W86A (5Ј-G CTG TGG ATC GTC TGC GCT GCA GAC CTC TTC TAC TC-3Ј), W94A (5Ј-C CTC TTC TAC TCT TTC GCG GAA AGA AGT CGG GGC-3Ј), W142A (5Ј-GGG ATC ATG CTC ACT TTC GCA CTG GTA GCC CTA ATG TG-3Ј), W142F (5Ј-G CTC ACT TTT TTC CTG GTA GCC C-3Ј); MSD2 Trp mutants W361A (5Ј-C ACG AAG GCC CCA GAT GCG CAG GGC TAC TTC TAC-3Ј), W445A (5Ј-G TAC ATT AAC ATG ATC GCG TCA GCC CCC CTG CAA G-3Ј), W445F (5Ј-CG TAC ATT AAC ATG ATC TTC TCA GCC CCC CTG CAA GTC-3Ј), W445Y (5Ј-CC ACG TAC ATT AAC ATG ATC TAC TCA GCG CCC CTG CAA GTC-3Ј), W459A (5Ј-GCT CTC TAC CTC CTG GCG CTG AAT CTG GGC CC-3Ј), W553A (5Ј-G GGC ACC TTC ACC GCG GTC TGC ACG CCC-3Ј), W553F (5Ј-G GGC ACC TTC ACC TTC GTC TGC ACG CCC-3Ј), W553Y (5Ј-GCC CTG GGC ACC TTC ACA TAT GTC TGC ACG CCC-3Ј; and MSD3 Trp mutants W1198A (5Ј-C GTG GCC AAC AGG GCG CTG GCC GTG CGG C-3Ј), W1198F (5Ј-GTG GCC AAC AGG TTC CTG GCC GTG CGG C-3Ј), W1198Y (5Ј-GTG GCC AAC AGG TAC CTG GCC GTG CGG C-3Ј).
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ABCC1 p.Trp445Tyr 12388549:48:951
status: NEW139 One mutant, W445Y, was reproducibly expressed at lower levels (approximately half) than the corresponding W445A and W445F mutants for reasons that are presently unclear.
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ABCC1 p.Trp445Tyr 12388549:139:12
status: NEW140 The most conservatively substituted MRP1-Trp445 mutant, W445Y, showed significant transport activity with respect to all five MRP1 substrates compared with the W445A mutant after correcting for differences in MRP1 expression levels.
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ABCC1 p.Trp445Tyr 12388549:140:56
status: NEW141 Thus, the LTC4 and E13SO4 transport activities of W445Y MRP1 were similar to those of wild-type MRP1, whereas transport of E217betaG, GSH, and MTX was 30-60% of wild-type activity (Fig. 6, B-F).
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ABCC1 p.Trp445Tyr 12388549:141:50
status: NEW142 The Phe-substituted Trp445 mutant, W445F, showed levels of transport intermediate between those of the W445A and W445Y mutants.
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ABCC1 p.Trp445Tyr 12388549:142:113
status: NEW189 Ala substitution of Trp1198 in MSD3 also resulted in a broad and profound decrease in MRP1 transport activity except for FIG. 6. ATP-dependent organic anion transport activity of wild-type and mutant MRP1 containing conservative Phe and Tyr substitutions of Trp1198 in TM16 of MSD3. A, immunoblot of membrane vesicles prepared from HEK293T cells transfected with empty vector (pcDNA3.1(-)), wild-type (WT-MRP1), and mutant (W445A, W445F, and W445Y; W553A, W553F and W553Y; W1198A, W1198F, and W1198Y) MRP1 cDNAs. MRP1 proteins were detected with monoclonal antibody QCRL-1, and relative levels of expression shown under the blot were estimated by densitometry.
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ABCC1 p.Trp445Tyr 12388549:189:442
status: NEW190 B-F, relative levels of 3 H-labeled organic anion uptake by the membrane vesicles shown in A enriched for wild-type MRP1 (solid bar), Trp 3 Phe-substituted MRP1 mutants (W445F, W553F, and W1198F; hatched bars), and Trp 3 Tyr-substituted MRP1 mutants (W445Y, W553Y, and W1198Y; open bars) were determined as described under "Experimental Procedures."
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ABCC1 p.Trp445Tyr 12388549:190:251
status: NEW