ABCG2 p.Cys603Tyr
| Predicted by SNAP2: | A: D (85%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (95%), I: D (91%), K: D (95%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (95%), R: D (95%), S: D (91%), T: D (91%), V: D (95%), W: D (95%), Y: D (95%), |
| Predicted by PROVEAN: | A: D, 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: D, 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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89 intensities of the 70-kDa BCRP monomeric mutant bands were similar to wild-type with the exception of PA/C603S and PA/C603Y, which had somewhat lower expression levels (Fig. 6a).
X
ABCG2 p.Cys603Tyr 16367905:89:118
status: VERIFIED143 (c) SN-38 sensitivity of parental PA317, PA/WT, PA/C603D, PA/C603Y, PA/ C603S and PA/C603A.
X
ABCG2 p.Cys603Tyr 16367905:143:61
status: VERIFIED