ABCG2 p.Cys55Ser
| Predicted by SNAP2: | A: N (72%), D: N (53%), E: N (57%), F: N (82%), G: N (78%), H: N (87%), I: N (78%), K: N (66%), L: N (82%), M: N (66%), N: N (78%), P: N (57%), Q: N (78%), R: N (78%), S: N (82%), T: N (78%), V: N (78%), W: N (72%), Y: N (82%), |
| Predicted by PROVEAN: | A: N, 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: N, T: D, V: D, W: D, Y: D, |
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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.Cys55Ser 16367905:58:72
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.Cys55Ser 16367905:67:29
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.Cys55Ser 16367905:108:12
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.Cys55Ser 16367905:130:19
status: VERIFIED