ABCB1 p.Ala718Cys
| Predicted by SNAP2: | C: N (72%), D: D (71%), E: D (71%), F: D (75%), G: N (53%), H: D (66%), I: D (63%), K: D (75%), L: D (66%), M: D (59%), N: D (59%), P: D (75%), Q: D (63%), R: D (71%), S: N (93%), T: N (61%), V: D (63%), W: D (75%), Y: D (75%), |
| Predicted by PROVEAN: | C: 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: N, T: D, V: D, W: D, Y: D, |
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[hide] The packing of the transmembrane segments of human... J Biol Chem. 2000 Feb 25;275(8):5253-6. Loo TW, Clarke DM
The packing of the transmembrane segments of human multidrug resistance P-glycoprotein is revealed by disulfide cross-linking analysis.
J Biol Chem. 2000 Feb 25;275(8):5253-6., 2000-02-25 [PMID:10681495]
Abstract [show]
Residues from several transmembrane (TM) segments of P-glycoprotein (P-gp) likely form the drug-binding site(s). To determine the organization of the TM segments, pairs of cysteine residues were introduced into the predicted TM segments of a Cys-less P-gp, and the mutant protein was subjected to oxidative cross-linking. In SDS gels, the cross-linked product migrated with a slower mobility than the native protein. The cross-linked products were not detected in the presence of dithiothreitol. Cross-linking was observed in 12 of 125 mutants. The pattern of cross-linking suggested that TM6 is close to TMs 10, 11, and 12, while TM12 is close to TMs 4, 5, and 6. In some mutants the presence of drug substrate colchicine, verapamil, cyclosporin A, or vinblastine either enhanced or inhibited cross-linking. Cross-linking was inhibited in the presence of ATP plus vanadate. These results suggest that the TM segments critical for drug binding must be close to each other and exhibit different conformational changes in response to binding of drug substrate or vanadate trapping of nucleotide. Based on these results, we propose a model for the arrangement of the TM segments.
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No. Sentence Comment
77 In these cross-linking experiments, the amount of oxidant was lowered by 10-fold (0.2 mM), and the minimum temperature required to induce cross-TABLE I Cross-linking analysis of P-gp Cross-linking of S993C (TM12) with residues in the following TM: TM1 TM2 TM3 TM4 TM5 M51C -a Y130C - G185C - G226C - I293C - V52C - I131C - I186C - L227C ϩb T294C - V53C - Q132C - G187C - S228C - A295C ϩ G54C - V133C - D188C - A229C - N296C - T55C - S134C - K189C - A230C - I297C - L56C - F135C - I190C - V231C ϩ S298C - A57C - W136C - G191C - W232C ϩ I299C ϩ A58C - C137C - M192C - A233C ϩ G300C - I59C - L138C - F193C - K234C - A301C - I60C - A139C - F194C - I235C ϩ A302C - H61C - A140C - Q195C - L236C ϩ F303C - G141C - S196C - S237C - L304C - Cross-linking of P350C (TM6) with residues in the following TM: TM7 TM8 TM9 TM10 TM11 F711C - F770C - A828C - I867C - A935C - V712C - F771C - I829C - I868C - H936C - V713C - L772C - G830C - A869C - I937C - G714C - Q773C - S831C - I870C - F938C - V715C - G774C - R832C - A871C - G939C ϩ F716C - F775C - L833C - G872C - I940C - C717C - T776C - A834C - V873C - T941C - A718C - F777C - V835C - V874C ϩ F942C - I719C - G778C - I836C - E875C ϩ S943C - I720C - K779C - T837C - M876C ϩ F944C - N721C - A780C - Q838C - K877C - T945C - G722C - G781C - N839C - M878C - Q946C - G723C - E782C - I840C - L879C - A947C - I783C - a -, no cross-linked product detected in SDS-PAGE. b ϩ, cross-linked product detected in SDS-PAGE.
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ABCB1 p.Ala718Cys 10681495:77:1151
status: NEW[hide] Transmembrane segment 7 of human P-glycoprotein fo... Biochem J. 2006 Oct 15;399(2):351-9. Loo TW, Bartlett MC, Clarke DM
Transmembrane segment 7 of human P-glycoprotein forms part of the drug-binding pocket.
Biochem J. 2006 Oct 15;399(2):351-9., 2006-10-15 [PMID:16813563]
Abstract [show]
P-gp (P-glycoprotein; ABCB1) protects us by transporting a broad range of structurally unrelated compounds out of the cell. Identifying the regions of P-gp that make up the drug-binding pocket is important for understanding the mechanism of transport. The common drug-binding pocket is at the interface between the transmembrane domains of the two homologous halves of P-gp. It has been shown in a previous study [Loo, Bartlett and Clarke (2006) Biochem. J. 396, 537-545] that the first transmembrane segment (TM1) contributed to the drug-binding pocket. In the present study, we used cysteine-scanning mutagenesis, reaction with an MTS (methanethiosulfonate) thiol-reactive analogue of verapamil (termed MTS-verapamil) and cross-linking analysis to test whether the equivalent transmembrane segment (TM7) in the C-terminal-half of P-gp also contributed to drug binding. Mutation of Phe728 to cysteine caused a 4-fold decrease in apparent affinity for the drug substrate verapamil. Mutant F728C also showed elevated ATPase activity (11.5-fold higher than untreated controls) after covalent modification with MTS-verapamil. The activity returned to basal levels after treatment with dithiothreitol. The substrates, verapamil and cyclosporin A, protected the mutant from labelling with MTS-verapamil. Mutant F728C could be cross-linked with a homobifunctional thiol-reactive cross-linker to cysteines I306C(TM5) and F343C(TM6) that are predicted to line the drug-binding pocket. Disulfide cross-linking was inhibited by some drug substrates such as Rhodamine B, calcein acetoxymethyl ester, cyclosporin, verapamil and vinblastine or by vanadate trapping of nucleotides. These results indicate that TM7 forms part of the drug-binding pocket of P-gp.
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No. Sentence Comment
74 Mutant Verapamil S50 (µM) Vinblastine S50 (µM) Colchicine S50 (µM) F711C 9.8 + - 1.1 2.3 + - 0.2 410 + - 20 V712C 10.0 + - 0.8 1.9 + - 0.2 320 + - 40 V713C 9.9 + - 1.3 1.8 + - 0.2 340 + - 40 G714C 14.1 + - 2.1 1.9 + - 0.3 410 + - 30 V715C 9.8 + - 1.3 1.8 + - 0.3 330 + - 40 F716C 10.1 + - 1.0 2.1 + - 0.1 340 + - 30 C717C 10.0 + - 1.5 2.3 + - 0.3 390 + - 20 A718C 10.5 + - 1.3 2.0 + - 0.1 330 + - 30 I719C 10.5 + - 1.5 1.9 + - 0.2 370 + - 30 I720C 12.4 + - 0.7 2.4 + - 0.2 390 + - 10 N721C 13.0 + - 1.2 1.7 + - 0.2 380 + - 40 G722C ND ND ND G723C 11.1 + - 0.4 2.0 + - 0.3 410 + - 20 L724C 12.0 + - 1.5 2.4 + - 0.3 340 + - 30 Q725C 11.7 + - 1.1 2.0 + - 0.1 390 + - 20 P726C 11.9 + - 1.0 1.9 + - 0.2 450 + - 30 A727C 21.2 + - 3.1 1.9 + - 0.2 480 + - 40 F728C 48.7 + - 2.2 2.7 + - 0.3 830 + - 90 A729C 34.3 + - 3.0 2.3 + - 0.2 760 + - 80 I730C 12.0 + - 1.1 2.0 + - 0.1 420 + - 30 I731C 13.5 + - 1.9 1.9 + - 0.2 410 + - 30 Cys-less 11.6 + - 1.3 2.1 + - 0.3 400 + - 40 into the endoplasmic reticulum during synthesis of the protein.
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ABCB1 p.Ala718Cys 16813563:74:373
status: NEW