ABCG2 p.Tyr645Phe
| Predicted by SNAP2: | A: D (66%), C: D (66%), D: D (91%), E: D (91%), F: N (66%), G: D (80%), H: D (85%), I: D (63%), K: D (91%), L: D (66%), M: D (63%), N: D (85%), P: D (91%), Q: D (85%), R: D (91%), S: D (80%), T: D (80%), V: D (66%), W: D (80%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: N, 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, |
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[hide] Transmembrane helices 1 and 6 of the human breast ... Am J Physiol Cell Physiol. 2010 Nov;299(5):C1100-9. Epub 2010 Aug 25. Ni Z, Bikadi Z, Cai X, Rosenberg MF, Mao Q
Transmembrane helices 1 and 6 of the human breast cancer resistance protein (BCRP/ABCG2): identification of polar residues important for drug transport.
Am J Physiol Cell Physiol. 2010 Nov;299(5):C1100-9. Epub 2010 Aug 25., [PMID:20739628]
Abstract [show]
The human breast cancer resistance protein (BCRP/ABCG2) mediates efflux of drugs and xenobiotics. In this study, we investigated the role of polar residues within or near the predicted transmembrane alpha-helices 1 and 6 of BCRP in drug transport. We substituted Asn(387), Gln(398), Asn(629), and Thr(642) with Ala, Thr(402) with Ala and Arg, and Tyr(645) with Phe, and the mutants were stably expressed in human embryonic kidney-293 or Flp-In-293 cells. Immunoblotting and confocal microscopy analysis revealed that all of the mutants were well expressed and predominantly targeted to the plasma membrane. While T402A and T402R showed a significant global reduction in the efflux of mitoxantrone, Hoechst 33342, and BODIPY-prazosin, N629A exhibited significantly increased efflux activities for all of the substrates. N387A and Q398A displayed significantly impaired efflux for mitoxantrone and Hoechst 33342, but not for BODIPY-prazosin. In contrast, T642A and Y645F showed a moderate reduction in Hoechst 33342 efflux only. Drug resistance profiles of human embryonic kidney-293 cells expressing the mutants generally correlated with the efflux data. Furthermore, N629A was associated with a marked increase, and N387A and T402A with a significant reduction, in BCRP ATPase activity. Mutations of some of the polar residues may cause conformational changes, as manifested by the altered binding of the 5D3 antibody to BCRP in the presence of prazosin. The inward-facing homology model of BCRP indicated that Thr(402) within transmembrane 1 may be important for helical interactions, and Asn(629) may be involved in BCRP-substrate interaction. In conclusion, we have demonstrated the functional importance of some of these polar residues in BCRP activity.
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No. Sentence Comment
9 We substituted Asn387 , Gln398 , Asn629 , and Thr642 with Ala, Thr402 with Ala and Arg, and Tyr645 with Phe, and the mutants were stably expressed in human embryonic kidney-293 or Flp-In-293 cells.
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ABCG2 p.Tyr645Phe 20739628:9:92
status: VERIFIED13 In contrast, T642A and Y645F showed a moderate reduction in Hoechst 33342 efflux only.
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ABCG2 p.Tyr645Phe 20739628:13:23
status: VERIFIED68 The forward primers used for mutagenesis were as follows: N387A (5=- AAG CGT TCA TTC AAA GCC TTG CTG GGT AAT CCC-3=), Q398A (5=-CAG GCC TCT ATA GCT GCG ATC ATT GTC ACA GTC-3=), T402A (5=-GCT CAG ATC ATT GTC GCA GTC GTA CTG GGA CTG-3=), N629A (5=-CTG GGG CTT GTG GAA GGC TCA CGT GGC CTT GGC TTG-3=), T642A (5=-GAT TGT TAT TTT CCT CGC AAT TGC CTA CCT GAA ATT G-3=), and Y645F (5=-TTC CTC ACA ATT GCC TTC CTG AAA TTG TTA TTT C-3=).
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ABCG2 p.Tyr645Phe 20739628:68:368
status: VERIFIED158 To evaluate functional importance of these polar residues in substrate specificity and overall transport activity of BCRP, we generated six mutants in which Asn387 , Gln398 , Thr402 , Asn629 , and Thr642 were replaced with Ala. Tyr645 was replaced with Phe to assess the role of potential hydrogen bond of this residue in drug transport, but with the minimal probability of introducing structural changes.
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ABCG2 p.Tyr645Phe 20739628:158:228
status: VERIFIED162 The levels of N387A, Q398A, T402A, N629A, T642A, and Y645F, determined by immunoblotting of whole cell lysates using beta-actin as an internal standard, were ϳ4.4-, 4.5-, 3.1-, 0.4-, 1.3-, and 1.5-fold that of wild-type BCRP (Fig. 2, A and B).
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ABCG2 p.Tyr645Phe 20739628:162:53
status: VERIFIED189 After normalization to the BCRP protein levels, neither T642A nor Y645F seem to affect the efflux of MX and BODIPY-prazosin compared with wild-type protein, except for a moderate decrease in the efflux of Hoechst 33342.
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ABCG2 p.Tyr645Phe 20739628:189:66
status: VERIFIED200 Representative areas of HEK-293 cells expressing wild-type BCRP and the mutants N387A, Q398A, T402A, N629A, T642A, and Y645F are shown.
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ABCG2 p.Tyr645Phe 20739628:200:119
status: VERIFIED224 The Km values of N387A, T402A, T642A, and Y645F were comparable to that of wild-type protein; however, the Km values of Q398A and N629A were decreased by ϳ50-60%.
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ABCG2 p.Tyr645Phe 20739628:224:42
status: VERIFIED229 The Vmax/Km values of Q398A, T642A, and Y645F were comparable to that of wild-type protein.
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ABCG2 p.Tyr645Phe 20739628:229:40
status: VERIFIED231 FTC-inhibitable efflux activities of HEK-293 cells stably expressing wild-type and mutant BCRP Mitoxantrone BODIPY-Prazosin Hoechst 33342 ⌬F ⌬F= Ratio ⌬F ⌬F= Ratio ⌬F ⌬F= Ratio Wild-type BCRP 10.6 Ϯ 0.6 10.6 Ϯ 0.6 1.0 12.5 Ϯ 4.3 12.5 Ϯ 4.3 1.0 2150.0 Ϯ 25.5 2150.0 Ϯ 25.5 1.0 N387A 11.3 Ϯ 0.5 2.5 Ϯ 0.1* 0.2 54.5 Ϯ 5.8 12.3 Ϯ 1.3 1.0 5,024.7 Ϯ 570.5 1,131.7 Ϯ 128.5* 0.5 Q398A 28.1 Ϯ 5.2 6.3 Ϯ 1.2* 0.6 69.3 Ϯ 10.6 15.5 Ϯ 2.4 1.2 4,206.7 Ϯ 252.1 941.1 Ϯ 56.4* 0.4 T402A 12.3 Ϯ 2.4 4.0 Ϯ 0.8* 0.4 4.5 Ϯ 1.8 1.5 Ϯ 0.6* 0.1 999.3 Ϯ 352.9 322.4 Ϯ 113.8* 0.1 N629A 19.3 Ϯ 3.7 46.0 Ϯ 8.8* 4.3 12.8 Ϯ 1.5 30.5 Ϯ 3.6* 2.4 2,681.0 Ϯ 370.5 6,383.3 Ϯ 882.1* 3.0 T642A 17.0 Ϯ 0.3 12.9 Ϯ 0.2 1.2 15.4 Ϯ 1.3 11.8 Ϯ 1.0 0.9 1,860.7 Ϯ 462.3 1,420.4 Ϯ 352.9* 0.7 Y645F 16.8 Ϯ 2.3 11.6 Ϯ 1.6 1.1 15.1 Ϯ 4.6 10.4 Ϯ 3.2 0.8 1,358.7 Ϯ 35.5 937.0 Ϯ 24.5* 0.4 Values are means Ϯ SD of 3 independent experiments.
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ABCG2 p.Tyr645Phe 20739628:231:1004
status: VERIFIED238 Relative drug resistance of HEK-293 cells expressing wild-type and mutant BCRP MX SN-38 Dox Rho-123 IC50, nM RR (ratio) IC50, nM RR (ratio) IC50, nM RR IC50, nM RR pcDNA control 8.5 Ϯ 0.6 2.3 Ϯ 0.28 125.6 Ϯ 32.0 1,881 Ϯ 168.2 Wild-type BCRP 64.8 Ϯ 3.9 7.6 (1.0) 89.7 Ϯ 5.4 39.0 (1.0) 168.0 Ϯ 24.5 1.3 3,341 Ϯ 267.4 1.8 N387A 54.8 Ϯ 6.3 6.4 (0.2)* 44.8 Ϯ 6.3 19.5 (0.1)* 120.4 Ϯ 31.6 1.0 3,279 Ϯ 436.8 1.7 Q398A 49.9 Ϯ 4.6 5.9 (0.2)* 71.6 Ϯ 4.3 31.1 (0.2)* 173.4 Ϯ 36.5 1.4 2,534 Ϯ 376.5 1.3 T402A 43.3 Ϯ 7.6 5.1 (0.2)* 63.0 Ϯ 5.4 27.4 (0.2)* 129.4 Ϯ 31.4 1.0 2,140 Ϯ 210.7 1.1 N629A 76.5 Ϯ 12.3 9.0 (2.8)* 108.3 Ϯ 12.3 47.1 (2.9)* 164.6 Ϯ 14.8 1.3 3,051 Ϯ 286.5 1.6 T642A 50.0 Ϯ 9.5 5.9 (0.6) 49.9 Ϯ 9.9 21.7 (0.4)* 156.1 Ϯ 20.0 1.2 1,393 Ϯ 221.6 0.7 Y645F 42.8 Ϯ 6.8 5.0 (0.5)* 44.8 Ϯ 6.3 19.5 (0.3)* 132.4 Ϯ 18.4 1.1 1,846 Ϯ 206.2 1.0 The IC50 values shown are means Ϯ SD of 3 independent experiments.
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ABCG2 p.Tyr645Phe 20739628:238:919
status: VERIFIED250 Only a slight decrease in 5D3-phycoerythrin fluorescence was observed for the vector control cells (Fig. 5); however, the 5D3-phycoerythrin fluorescence was differentially increased in a prazosin concentration-dependent manner for wild-type BCRP, N629A, T642A, and Y645F.
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ABCG2 p.Tyr645Phe 20739628:250:265
status: VERIFIED274 Kinetic parameters of ATP hydrolysis by wild-type and mutant BCRP Wild-type BCRP N387A Q398A T402A N629A T642A Y645F Vmax, nmol Pi ·min-1 ·mg protein-1 14.5 Ϯ 1.9 16.9 Ϯ 1.5 14.9 Ϯ 0.93 17.4 Ϯ 1.7 11.5 Ϯ 1.1 17.9 Ϯ 1.9 14.5 Ϯ 1.9 Vmax normalized to BCRP protein level, nmol Pi ·min-1 ·mg protein-1 14.5 Ϯ 1.9 7.0 Ϯ 0.63 6.5 Ϯ 0.41 8.3 Ϯ 0.81 28.0 Ϯ 2.7 16.3 Ϯ 1.7 12.0 Ϯ 1.6 Km for ATP, mM 0.89 Ϯ 0.40 0.90 Ϯ 0.27 0.48 Ϯ 0.12 1.1 Ϯ 0.35 0.40 Ϯ 0.15 0.93 Ϯ 0.34 0.89 Ϯ 0.43 Vmax/Km, nmol Pi ·min-1 ·mg protein-1 ·mM-1 16.3 7.8 13.5 7.5 70.0 17.5 13.5 Values are means Ϯ SD of 3 independent determinations.
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ABCG2 p.Tyr645Phe 20739628:274:111
status: VERIFIED339 A conservative mutation of Tyr645 to Phe and Ala substitution of Thr642 caused only moderate changes in drug efflux and resistance that were restricted to Hoechst 33342 and SN-38 (Tables 1 and 2).
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ABCG2 p.Tyr645Phe 20739628:339:27
status: VERIFIED350 Prazosin differentially increased 5D3 binding to wild-type BCRP, N629A, T642A, and Y645F, whereas 5D3 binding to N387A and Q398A was slightly decreased (Fig. 5).
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ABCG2 p.Tyr645Phe 20739628:350:83
status: VERIFIED[hide] Mutations of the central tyrosines of putative cho... Biochim Biophys Acta. 2015 Feb;1848(2):477-87. doi: 10.1016/j.bbamem.2014.11.006. Epub 2014 Nov 14. Gal Z, Hegedus C, Szakacs G, Varadi A, Sarkadi B, Ozvegy-Laczka C
Mutations of the central tyrosines of putative cholesterol recognition amino acid consensus (CRAC) sequences modify folding, activity, and sterol-sensing of the human ABCG2 multidrug transporter.
Biochim Biophys Acta. 2015 Feb;1848(2):477-87. doi: 10.1016/j.bbamem.2014.11.006. Epub 2014 Nov 14., [PMID:25445676]
Abstract [show]
Human ABCG2 is a plasma membrane glycoprotein causing multidrug resistance in cancer. Membrane cholesterol and bile acids are efficient regulators of ABCG2 function, while the molecular nature of the sterol-sensing sites has not been elucidated. The cholesterol recognition amino acid consensus (CRAC, L/V-(X)(1-5)-Y-(X)(1-5)-R/K) sequence is one of the conserved motifs involved in cholesterol binding in several proteins. We have identified five potential CRAC motifs in the transmembrane domain of the human ABCG2 protein. In order to define their roles in sterol-sensing, the central tyrosines of these CRACs (Y413, 459, 469, 570 and 645) were mutated to S or F and the mutants were expressed both in insect and mammalian cells. We found that mutation in Y459 prevented protein expression; the Y469S and Y645S mutants lost their activity; while the Y570S, Y469F, and Y645F mutants retained function as well as cholesterol and bile acid sensitivity. We found that in the case of the Y413S mutant, drug transport was efficient, while modulation of the ATPase activity by cholesterol and bile acids was significantly altered. We suggest that the Y413 residue within a putative CRAC motif has a role in sterol-sensing and the ATPase/drug transport coupling in the ABCG2 multidrug transporter.
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No. Sentence Comment
5 We found that mutation in Y459 prevented protein expression; the Y469S and Y645S mutants lost their activity; while the Y570S, Y469F, and Y645F mutants retained function as well as cholesterol and bile acid sensitivity.
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ABCG2 p.Tyr645Phe 25445676:5:138
status: NEW114 We found that the Y469F and Y645F mutants were active (Fig. 2B), indicating the importance of the phenyl ring, but not of a hydroxyl group at these positions for protein function.
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ABCG2 p.Tyr645Phe 25445676:114:28
status: NEW120 We found that the basal ATPase activity of the Y469F, Y570S and Y645F mutants showed a moderate (approximately 20%, p b 0.05) increase upon cholesterol addition, while the substrate stimulated ATP hydrolysis of the same mutants was significantly (50-100% increase, p b 0.01) accelerated by cholesterol loading (Fig. 2C).
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ABCG2 p.Tyr645Phe 25445676:120:64
status: NEW174 generated mammalian HEK 293 cells stably expressing the Y413S, Y469F, Y570S and Y645F mutants.
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ABCG2 p.Tyr645Phe 25445676:174:80
status: NEW233 Previously, the Y645F mutation has been found to be functional, although has shown slightly decreased Hoechst 33342 transport capacity [39].
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ABCG2 p.Tyr645Phe 25445676:233:16
status: NEW250 BODIPY-prazosin Pheophorbide A Hoechst 33342 mitoxantrone wtABCG2 + + + + Y413S + + + + Y469F + + + + Y570S + + + + Y645F + + + + Fig. 8.
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ABCG2 p.Tyr645Phe 25445676:250:116
status: NEW