ABCG2 p.Cys43Ser
| Predicted by SNAP2: | A: N (66%), D: D (66%), E: D (59%), F: N (53%), G: D (53%), H: N (72%), I: N (53%), K: D (53%), L: D (53%), M: D (53%), N: N (66%), P: D (66%), Q: N (57%), R: D (53%), S: N (78%), T: N (66%), V: N (61%), W: D (71%), Y: N (66%), |
| Predicted by PROVEAN: | A: N, D: N, E: N, F: N, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: N, W: N, Y: N, |
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[hide] Role of Cys-603 in dimer/oligomer formation of the... Cancer Sci. 2005 Dec;96(12):866-72. Kage K, Fujita T, Sugimoto Y
Role of Cys-603 in dimer/oligomer formation of the breast cancer resistance protein BCRP/ABCG2.
Cancer Sci. 2005 Dec;96(12):866-72., [PMID:16367905]
Abstract [show]
Breast cancer resistance protein (BCRP/ABCG2) is a half-molecule ATP-binding cassette transporter that we have previously suggested might function as a homodimer, bridged by disulfide bonds. In the present study, we carried out cysteine-scanning mutagenesis, substituting Ser for Cys, and established 12 PA317 transfectants expressing BCRP mutants with possible disruptions to their S-S bonds. Western blot analysis of BCRP from the wild-type transfectants (PA/WT) confirmed that the wild-type protein migrates as a 140-kDa dimer under non-reducing conditions, but as a 70-kDa monomer under reducing conditions. However, under non-reducing conditions the BCRP-C603S mutant migrated both as a 70-kDa monomer and a 140-kDa dimer, whereas all other mutant BCRP migrated only as dimers. PA317 cells transfected with C603S-BCRP (PA/C603S) showed either similar or only marginally lower SN-38 resistance than PA/WT cells, despite the reduced levels of BCRP dimer in these cells. Moreover, the degree of SN-38 resistance in the mutant BCRP transfectants was found to be associated with the monomer expression levels under reducing conditions. Reverse transcription-polymerase chain reaction analysis showed that the BCRP mRNA levels were similar in the transfectants. We subsequently generated six C603X mutants of BCRP (X=D, H, R, Y, A and W) and carried out western blot analysis and drug sensitivity assays. The results were equivalent to those from the PA/C603S cells, with some variations that again corresponded to the monomer levels. Our findings suggest that Cys-603 is an important residue in the covalent bridge between BCRP monomers but that a functioning unit of BCRP may not necessarily require covalent linkages.
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No. Sentence Comment
58 Also under reducing conditions, the BCRP protein levels in PA/ C43S, PA/C55S, PA/C284S and PA/C603S cells were slightly lower than the levels in the wild-type transfectants.
X
ABCG2 p.Cys43Ser 16367905:58:63
status: VERIFIED67 In contrast, the PA/C43S, PA/C55S, PA/C284S and PA/C603S mutants expressed intermediate amounts of BCRP and, in PA/C438S cells, little surface expression of BCRP was observed.
X
ABCG2 p.Cys43Ser 16367905:67:20
status: VERIFIED108 PA/C43S, PA/C55S, PA/C284S and PA/C603S transfectants acquired similar or somewhat lower degrees of SN-38 resistance than PA/WT cells.
X
ABCG2 p.Cys43Ser 16367905:108:3
status: VERIFIED130 In contrast, C43S, C55S and C284S mutations did not interfere with the overall function of BCRP, as these mutants conferred high levels of resistance to SN-38 (Fig. 5b).
X
ABCG2 p.Cys43Ser 16367905:130:13
status: VERIFIED