ABCG2 p.Cys544Ser
| Predicted by SNAP2: | A: N (78%), D: D (71%), E: D (66%), F: N (57%), G: N (57%), H: D (59%), I: N (61%), K: D (71%), L: N (57%), M: N (53%), N: D (53%), P: D (63%), Q: D (59%), R: D (66%), S: N (72%), T: N (72%), V: N (66%), W: D (66%), Y: N (66%), |
| Predicted by PROVEAN: | A: N, D: D, E: D, F: N, G: D, H: N, I: N, K: N, L: N, M: N, N: N, P: D, 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
66 For the PA/C119S, PA/C374S, PA/C491S, PA/C544S and PA/C635S species, these exogenous mutant protein levels were equivalent to PA/WT.
X
ABCG2 p.Cys544Ser 16367905:66:41
status: VERIFIED73 Transfectants expressing a high level of exogenous BCRP mutant, including PA/C544S and PA/ C635S, showed almost the same degree of resistance as PA/ WT cells.
X
ABCG2 p.Cys544Ser 16367905:73:77
status: VERIFIED