ABCMdb

ABCC1 p.Trp459Ala

Predicted by SNAP2:	A: D (63%), C: D (53%), D: D (80%), E: D (75%), F: N (53%), G: D (75%), H: D (63%), I: D (66%), K: D (80%), L: D (71%), M: D (63%), N: D (75%), P: D (85%), Q: D (75%), R: D (80%), S: D (66%), T: D (75%), V: D (63%), Y: N (57%),
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). Login to comment
108 All four mutants generated (W361A, W445A, W459A, and W553A) were expressed at levels 60-90% those of wild-type MRP1, indicating that none of the mutations had a major effect on the expression levels of the protein. Login to comment
110 After 1 min, ATP-dependent [3 H]LTC4 uptake by the W445A and W553A MRP1 mutants was reduced by ϳ75 and 50%, respectively, whereas uptake by the W361A and W459A mutants was comparable with wild-type MRP1 (Fig. 3B). Login to comment
112 The ATP-dependent uptake rate of this substrate by the W459A MRP1 mutant, as for LTC4 uptake, was comparable with that of wild-type MRP1 (Fig. 3C). Login to comment
119 Similarly, GSH-stimulated E13SO4 uptake levels by the W445A and W553A mutants were just 30 and Ͻ10% of wild-type MRP1 levels, respectively, whereas uptake by the W361A mutant was similar to wild-type MRP1, and uptake by W459A MRP1 was reduced by just 25% (Fig. 4B). Login to comment
121 A, ATP-dependent uptake of [3 H]LTC4 was measured in membrane vesicles prepared from HEK293T cells transfected with empty vector pcDNA3.1(-) (E) and vectors containing wild-type MRP1 (f) and MSD2 Trp-Ala mutant MRP1 cDNAs (W361A, Œ; W445A, ; W459A, ࡗ; and W553A, q). Login to comment
124 C, the time course of ATP-dependent uptake of [3 H]E217betaG by wild-type MRP1 and MSD2 mutants W361A, W445A, W459A, and W553A was measured as described for A. D, relative levels of [3 H]E217betaG uptake at 1 min are shown and were determined from the time course shown in C as described for B. Login to comment
127 MTX uptake by the W361A mutant was also reduced (ϳ40%), whereas uptake by the W459A mutant was similar to that of wild-type MRP1. Login to comment
153 Relative uptake levels of 3 H-labeled organic anions by membrane vesicles enriched for wild-type MRP1 (solid bar) and W361A, W445A, W459A, and W553A mutant MRP1 proteins (shaded bars) were determined as described under "Experimental Procedures." Login to comment
180 The W459A mutant displayed a slightly different phenotype in that its LTC4, E217betaG, and MTX transport activities were similar to wild-type MRP1, but GSH and E13SO4 transport activities were reduced by 25-50%. Login to comment