ABCG2 p.Gly410Ala
| Predicted by SNAP2: | A: D (80%), C: D (75%), D: D (91%), E: D (95%), F: D (91%), H: D (95%), I: D (91%), K: D (95%), L: D (91%), M: D (91%), N: D (91%), P: D (91%), Q: D (91%), R: D (95%), S: D (71%), T: D (91%), V: D (91%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: 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: D, |
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[hide] Mutational analysis of ABCG2: role of the GXXXG mo... Biochemistry. 2004 Jul 27;43(29):9448-56. Polgar O, Robey RW, Morisaki K, Dean M, Michejda C, Sauna ZE, Ambudkar SV, Tarasova N, Bates SE
Mutational analysis of ABCG2: role of the GXXXG motif.
Biochemistry. 2004 Jul 27;43(29):9448-56., 2004-07-27 [PMID:15260487]
Abstract [show]
ABCG2 (BCRP/MXR/ABCP) is a half-transporter associated with multidrug resistance that presumably homodimerizes for function. It has a conserved GXXXG motif in its first transmembrane segment, a motif that has been linked with dimerization in other proteins, e.g., glycophorin A. We substituted either or both glycines of this GXXXG motif with leucines to evaluate the impact on drug transport, ATP hydrolysis, cross-linking, and susceptibility to degradation. All mutants also carried the R482G gain-of-function mutation, and all migrated to the cell surface. The mutations resulted in lost transport for rhodamine 123 and impaired mitoxantrone, pheophorbide a, and BODIPY-prazosin transport, particularly in the double leucine mutant (G406L/G410L). Basal ATPase activity of the G406L/G410L mutant was comparable to the empty vector transfected cells with no substrate induction. Despite impaired function, the mutants retained susceptibility to cross-linking using either disuccinimidyl suberate (DSS) or the reducible dithiobis(succinimidyl propionate) (DSP) and demonstrated a high molecular weight complex under nonreducing conditions. Mutations to alanine at the same positions yielded fully functional transporters. Finally, we exposed cells to mitoxantrone to promote folding and processing of the mutant proteins, which in the leucine mutants resulted in increased amounts detected on immunoblot and by immunofluorescence. These studies support a hypothesis that the GXXXG motif promotes proper packing of the transmembrane segments in the functional ABCG2 homodimer, although it does not solely arbitrate dimerization.
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No. Sentence Comment
55 The following ABCG2 mutants were generated: G406L, G410L, G406L/G410L, G406A, G410A, and G406A/ G410A.
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ABCG2 p.Gly410Ala 15260487:55:78
status: VERIFIEDX
ABCG2 p.Gly410Ala 15260487:55:96
status: VERIFIED145 Transport studies for the GXXXG alanine mutants using the same ABCG2 substrates were also performed; Figure 3 shows the results obtained with the G406A/G410A mutant.
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ABCG2 p.Gly410Ala 15260487:145:152
status: VERIFIED146 Changes in fluorescence when FTC was added were almost identical to the R482G mutant, indicating that alanine is able to replace glycine without interfering with protein function. Flow cytometry also proved that the G406A and G410A mutants had intact transport of these substrates (data not shown).
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ABCG2 p.Gly410Ala 15260487:146:226
status: VERIFIED161 Transport capacity for BODIPY-prazosin, rhodamine 123, mitoxantrone, and pheohorbide A in the R482G, G406A/G410A, G406L/G410L, G406L, and G410L transfected cells. Plots: Accumulation without FTC (s) and with FTC (---).
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ABCG2 p.Gly410Ala 15260487:161:107
status: VERIFIED164 The G406A/G410A mutants show intact transport capacity for all studied substrates.
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ABCG2 p.Gly410Ala 15260487:164:10
status: VERIFIED170 (D) Similar results were obtained for the G406L and G410A mutants.
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ABCG2 p.Gly410Ala 15260487:170:52
status: VERIFIED174 Identical results were obtained with all the leucine and alanine mutants (Figure 4C showing results for the G406A and G410L mutants and Figure 4D for G406L and G410A; similar data not shown for the G406L/G410L and G406A/G410A mutants), implying that even if dimerization is impaired in these mutants, it has not prevented their close association on the cell surface.
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ABCG2 p.Gly410Ala 15260487:174:160
status: VERIFIEDX
ABCG2 p.Gly410Ala 15260487:174:220
status: VERIFIED[hide] Towards understanding the mechanism of action of t... J Mol Graph Model. 2007 Mar;25(6):837-51. Epub 2006 Aug 30. Li YF, Polgar O, Okada M, Esser L, Bates SE, Xia D
Towards understanding the mechanism of action of the multidrug resistance-linked half-ABC transporter ABCG2: a molecular modeling study.
J Mol Graph Model. 2007 Mar;25(6):837-51. Epub 2006 Aug 30., [PMID:17027309]
Abstract [show]
The ATP-binding cassette protein ABCG2 is a member of a broad family of ABC transporters with potential clinical importance as a mediator of multidrug resistance. We carried out a homology and knowledge-based, and mutationally improved molecular modeling study to establish a much needed structural framework for the protein, which could serve as guidance for further genetic, biochemical, and structural analyses. Based on homology with known structures of both full-length and nucleotide-binding domains (NBD) of ABC transporters and structural knowledge of integral membrane proteins, an initial model of ABCG2 was established. Subsequent refinement to conform to the lipophilic index distributions in the transmembrane domain (TMD) and to the results of site-directed mutagenesis experiments led to an improved model. The complete ABCG2 model consists of two identical subunits facing each other in a closed conformation. The dimeric interface in the nucleotide-binding domain (NBD) involves a characteristic nucleotide sandwich and the interface in the TMD consists of the TM helices 1-3 of one subunit and the helices 5 and 6 of the other. The interface between the NBD and the TMD is bridged by the conserved structural motif between TM2 and TM3, the intracellular domain 1 (ICD1), and the terminal beta-strand (S6) of the central beta-sheet in the NBD. The apparent flexibility of the ICD1 may play a role in transmitting conformational changes from the NBD to the TMD or from the TMD to the NBD.
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No. Sentence Comment
177 Exhibit reduced transport of mitoxantrone, pheophorbide and basal ATPase activity [17] G406A, G410A, G406A/G410A TM1 Fully functional b E446A,D,G,H,K,R,S TM2 Loss of drug resistance [21] R482G,T,M,S, N,D,K,Y TM3 T or G change produces gain of function mutant.
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ABCG2 p.Gly410Ala 17027309:177:94
status: VERIFIEDX
ABCG2 p.Gly410Ala 17027309:177:107
status: VERIFIED[hide] Determinants of the activity and substrate recogni... Drug Metab Rev. 2014 Nov;46(4):459-74. doi: 10.3109/03602532.2014.942037. Epub 2014 Jul 18. Szafraniec MJ, Szczygiel M, Urbanska K, Fiedor L
Determinants of the activity and substrate recognition of breast cancer resistance protein (ABCG2).
Drug Metab Rev. 2014 Nov;46(4):459-74. doi: 10.3109/03602532.2014.942037. Epub 2014 Jul 18., [PMID:25036722]
Abstract [show]
The xenobiotic transporters are among the most important constituents of detoxification system in living organisms. Breast cancer resistance protein (BCRP/ABCG2) is one of the major transporters involved in the efflux of xenobiotics. To understand its role in chemotherapeutic and multidrug resistance, it is crucial to establish the determinants of its substrate specificity, which obviously is of high relevance for successful therapy of many diseases. This article summarizes the current knowledge about the substrate preferences of BCRP. We overview the factors which determine its activity, inhibition and substrate recognition, focusing on the structural features of the transporter. BCRP substrate specificity is quite low as it interacts with a spectrum of substances with only a few common features: hydrophobic and aromatic regions, possibly a flat conformation and the metal ion-, oxygen- and nitrogen-containing functionalities, most of which may be the donors/acceptors of H-bonds. Several amino acid residues and structural motifs are responsible for BCRP activity and substrate recognition. Thus, the active form of BCRP, at least a dimer or a larger oligomer is maintained by intramolecular disulfide bridge that involves Cys(603) residues. The GXXXG motif in transmembrane helix 1, Cys residues, Arg(482) and Lys(86) are responsible for maintaining the protein structure, which confers transport activity, and the His(457) or Arg(456) residues are directly involved in substrate binding. Arg(482) does not directly bind substrates, but electrostatically interacts with charged molecules, which initiates the conformational changes that transmit the signal from the transmembrane regions to the ABC domain.
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No. Sentence Comment
209 Position Type of mutation Effect on the transporter References NBD Lys 86 Met (i) No stimulation of the ATPase activity by prazosin; (ii) no influence on the transport of mitoxantrone Henriksen et al. (2005b) Glu 126 stop, Phe 208 Ser, Ser 248 Phe, Glu 334 stop Inability to transport hematoporphyrin Tamura et al. (2006) Glu 211 Gln Complete abolishment of the ATPase activity and methotrexate transport Hou et al. (2009) Pro 392 Ala Significant reduction in the efflux activity of mitoxantrone, BODIPY-prazosin and Hoechst 33342 Ni et al. (2011) TM1 Gly 406 Ala Gly 410 Ala No influence on the activity of the transporter Polgar et al. (2004) Gly 406 Leu Gly 410 Leu (i) Loss of the ability to transport rhodamine123; (ii) impaired transport of mitoxantrone, Pheide and BODIPY-prazosin Polgar et al. (2004) Extracellular loop 1 Phe 431 Leu (i) Loss of the ability to transport methotrexate; (ii) 10% level of hematoporphyrin transport compared to the WT protein Tamura et al. (2006) Ser 441 Asn Inability to transport hematoporphyrin Tamura et al. (2006) Ser 441 Asn Loss of the ability to transport methotrexate Tamura et al. (2006) TM2 Lys 452 Ala His 457 Ala Increase in transport of mitoxantrone, BODIPY-prazosin and Hoechst 33342 Cai et al. (2010) Lys 453 Ala Arg 465 Ala Decrease in transport of mitoxantrone, BODIPY-prazosin, Hoechst 33342, doxorubicin, SN-38 and rhodamine 123 Cai et al. (2010) TM3 Arg 482 Gly Arg 482 Thr (i) No change in the inhibitory activity of lapatinib; (ii) about two times greater inhibition by ritonavir, saquinavir and nalfinavir than in the WT variant; (iii) gaining the ability to transport rhodamine123 and doxorubicin; (iv) no influence on the transport of mitoxantrone; (v) loss of the ability to transport methotrexate Dai et al. (2008), Gupta et al. (2004), Honjo et al. (2001), Mitomo et al. (2003) Arg 482 Thr (i) Lower IC 50 of cyclosporine A for mutant than for WT variant; (ii) lower elacridar inhibition potency Xia et al. (2007) Arg 482 Lys Complete loss of transport activity Ejendal et al. (2006) Phe 489 Leu Impaired transport of porphyrins, no transport of methotrexate Tamura et al. (2006) Extracellular loop 3 Asn 590 Tyr Over twice reduced transport of mitoxantrone, topotecan, daunorubicin and rhodamine 123 Vethanayagam et al. (2005) Cys 592 Ala/Cys 608 Ala (i) Transport of mitoxantrone almost unchanged; (ii) transport of BODIPY-prazosin significantly impaired Henriksen et al. (2005a) Extracellular loop 3 Cys 603 Ser Cys 592 Ser/Cys 608 Ser Cys 592 Ser/Cys 603 Ser/Cys 608 Ser Diminished susceptibility to the inhibitory activity of fumitremorgin C Shigeta et al. (2010) Cys-less Arg 482 Gly-BCRP Complete loss of the ability to efflux mitoxantrone Liu et al. (2008b) The positions of the amino acid residues refer to the topological model of BCRP proposed by Wang et al. (2009).
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ABCG2 p.Gly410Ala 25036722:209:564
status: NEW