ABCB1 p.Ile940Cys
| Predicted by SNAP2: | A: N (78%), C: N (87%), D: D (71%), E: D (66%), F: N (93%), G: D (53%), H: D (59%), K: D (66%), L: N (97%), M: N (93%), N: D (63%), P: D (63%), Q: D (59%), R: D (63%), S: N (78%), T: N (61%), V: N (93%), W: D (53%), Y: D (53%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: N, G: D, H: D, K: D, L: N, M: N, N: D, P: D, Q: D, R: D, S: D, T: D, V: N, 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.Ile940Cys 10681495:77:1103
status: NEW[hide] Val133 and Cys137 in transmembrane segment 2 are c... J Biol Chem. 2004 Apr 30;279(18):18232-8. Epub 2004 Jan 28. Loo TW, Bartlett MC, Clarke DM
Val133 and Cys137 in transmembrane segment 2 are close to Arg935 and Gly939 in transmembrane segment 11 of human P-glycoprotein.
J Biol Chem. 2004 Apr 30;279(18):18232-8. Epub 2004 Jan 28., 2004-04-30 [PMID:14749322]
Abstract [show]
P-glycoprotein (P-gp; ABCB1) transports a wide variety of structurally diverse compounds out of the cell. The protein has two homologous halves joined by a linker region. Each half consists of a transmembrane (TM) domain with six TM segments and a nucleotide-binding domain. The drug substrate-binding pocket is at the interface between the TM segments in each half of the protein. Preliminary studies suggested that the arrangement of the two halves of P-gp shows rotational symmetry (i.e. "head-to-tail" arrangement). Here, we tested this model by determining whether the cytoplasmic ends of TM2 and TM3 in the N-terminal half are in close contact with TM11 in the C-terminal half. Mutants containing a pair of cysteines in TM2/TM11 or TM3/TM11 were subjected to oxidative cross-linking with copper phenanthroline. Two of the 110 TM2/TM11 mutants, V133C(TM2)/G939C(TM11) and C137C(TM2)/A935C (TM11), were cross-linked at 4 degrees C, when thermal motion is reduced. Cross-linking was specific since no cross-linked product was detected in the 100 double Cys TM3/TM11 mutants. Vanadate trapping of nucleotide or the presence of some drug substrates inhibited cross-linking of mutants V133C(TM2)/G939C(TM11) and C137C(TM2)/A935C(TM11). Cross-linking of TM2 and TM11 also blocked drug-stimulated ATPase activity. The close proximity of TM2/TM11 and TM5/TM8 (Loo, T. W., Bartlett, M. C., and Clarke, D. M. (2004) J. Biol. Chem. 279, 7692-7697) indicates that these regions between the two halves must enclose the drug-binding pocket at the cytoplasmic side of P-gp. They may form the "hinges" required for conformational changes during the transport cycle.
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No. Sentence Comment
124 TABLE I Cross-linking between residues in TM2 and TM11 -, no cross-linked product detected on SDS-polyacrylamide gels at 37 °C; ϩ, relatively weak cross-linking (Ͻ50% of P-gp cross-linked) at 37 °C; ϩϩ, relatively strong cross-linking (Ͼ50% of P-gp cross-linked) at 37 °C; *, cross-linked product also detected at 22 °C; **, cross-linked product also detected at 22 and 4 °C. TM2 TM11 A935C H936C I937C F938C G939C I940C T941C F942C S943C F944C A128C - - - - - - - - - - A129C - - - - - - - - - - Y130C - - - - ϩ ϩ - ϩ ϩ - I131C - - - - - - - - - - Q132C - - - - - - - - - - V133C - - - ϩ ϩϩ, ** - - ϩ ϩ - S134C ϩ ϩ - - ϩ ϩ - - - - F135C - - - - - - - - - - W136C - - - - - - - - - - C137C ϩϩ, ** - - - ϩ - - - - - L138C ϩϩ, * - - - - - - - - - TM11 are close to each other at their cytoplasmic ends.
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ABCB1 p.Ile940Cys 14749322:124:470
status: NEW