ABCB1 p.His61Cys
| Predicted by SNAP2: | A: D (59%), C: N (57%), D: D (85%), E: D (85%), F: D (85%), G: D (75%), I: D (80%), K: D (85%), L: D (71%), M: D (85%), N: N (82%), P: D (91%), Q: D (75%), R: D (85%), S: N (66%), T: N (66%), V: D (80%), W: D (91%), Y: D (85%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, I: D, K: D, L: D, M: D, N: N, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] Transmembrane segment 1 of human P-glycoprotein co... Biochem J. 2006 Jun 15;396(3):537-45. Loo TW, Bartlett MC, Clarke DM
Transmembrane segment 1 of human P-glycoprotein contributes to the drug-binding pocket.
Biochem J. 2006 Jun 15;396(3):537-45., 2006-06-15 [PMID:16492138]
Abstract [show]
P-glycoprotein (P-gp; ABCB1) actively transports a broad range of structurally unrelated compounds out of the cell. An important step in the transport cycle is coupling of drug binding with ATP hydrolysis. Drug substrates such as verapamil bind in a common drug-binding pocket at the interface between the TM (transmembrane) domains of P-gp and stimulate ATPase activity. In the present study, we used cysteine-scanning mutagenesis and reaction with an MTS (methanethiosulphonate) thiol-reactive analogue of verapamil (MTS-verapamil) to test whether the first TM segment [TM1 (TM segment 1)] forms part of the drug-binding pocket. One mutant, L65C, showed elevated ATPase activity (10.7-fold higher than an untreated control) after removal of unchanged MTS-verapamil. The elevated ATPase activity was due to covalent attachment of MTS-verapamil to Cys65 because treatment with dithiothreitol returned the ATPase activity to basal levels. Verapamil covalently attached to Cys65 appears to occupy the drug-binding pocket because verapamil protected mutant L65C from modification by MTS-verapamil. The ATPase activity of the MTS-verapamil-modified mutant L65C could not be further stimulated with verapamil, calcein acetoxymethyl ester or demecolcine. The ATPase activity could be inhibited by cyclosporin A but not by trans-(E)-flupentixol. These results suggest that TM1 contributes to the drug-binding pocket.
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No. Sentence Comment
97 Table 1 shows that all mutants, except for mutants H61C and G64C, showed characteristics similar to that Table 1 Drug-stimulated ATPase activity of TM1 cysteine mutants ND, not determined because of very low expression.
X
ABCB1 p.His61Cys 16492138:97:51
status: NEW98 Verapamil Colchicine Vinblastine Mutant Vmax (%)* S50 (µM)† Vmax (%) S50 (µM) Vmax (%) S50 (µM) M51C 101 11.0 + - 0.6 96 391 + - 36 94 2.4 + - 0.2 V52C ND ND ND ND ND ND V53C 104 12.0 + - 0.2 101 389 + - 30 102 2.2 + - 0.1 G54C ND ND ND ND ND ND T55C 114 10.3 + - 1.1 95 418 + - 22 91 2.2 + - 0.1 L56C 103 12.2 + - 0.3 87 440 + - 41 95 2.5 + - 0.2 A57C 108 11.3 + - 0.3 98 377 + - 34 92 2.4 + - 0.2 A58C 90 12.5 + - 0.2 94 434 + - 20 95 2.6 + - 0.3 I59C 115 11.2 + - 0.8 95 380 + - 33 114 2.5 + - 0.2 I60C 102 11.1 + - 0.7 91 408 + - 18 110 2.5 + - 0.2 H61C 97 54.0 + - 5.0 61 912 + - 86 105 5.4 + - 0.4 G62C ND ND ND ND ND ND A63C 114 10.5 + - 1.2 99 362 + - 42 105 2.0 + - 0.3 G64C 106 45.0 + - 6.0 88 613 + - 55 60 2.4 + - 0.1 L65C 72 9.3 + - 1.1 112 368 + - 32 78 2.0 + - 0.2 P66C 95 13.0 + - 0.5 86 480 + - 39 97 2.8 + - 0.4 L67C 101 12.3 + - 0.3 106 423 + - 21 100 2.3 + - 0.1 M68C 119 9.7 + - 1.1 105 365 + - 32 92 2.3 + - 0.2 M69C 107 11.8 + - 0.6 110 431 + - 25 108 2.2 + - 0.1 L70C 94 11.4 + - 0.7 90 413 + - 18 98 2.3 + - 0.1 V71C 106 11.9 + - 0.3 90 370 + - 27 102 2.5 + - 0.5 Cys-less 100 12.0 + - 1.0 100 412 + - 48 100 2.2 + - 0.3 * Maximum activity relative to that of Cys-less P-gp.
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ABCB1 p.His61Cys 16492138:98:575
status: NEW101 Mutants H61C and G64C showed approx.
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ABCB1 p.His61Cys 16492138:101:8
status: NEW103 Mutant H61C also exhibited a reduction in the apparent affinity for vinblastine.
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ABCB1 p.His61Cys 16492138:103:7
status: NEW199 We also found that mutation of either His61 or Gly64 to cysteine altered the apparent affinity of P-gp for verapamil, colchicine or vinblastine (Table 1).
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ABCB1 p.His61Cys 16492138:199:38
status: NEW200 Arrangement of the residues in TM1 in a cylindrical helix (Figure 8A) shows that residues that react with MTS-verapamil (L65C; the present study) show alterations in substrate specificity when mutated (H61C, G644C and L65C; [44,45]) or show ATP-dependent cross-linking (M68 and M69; [30]) and occupy one face of the helix.
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ABCB1 p.His61Cys 16492138:200:202
status: NEW215 Residues that show alterations in substrate specificity when mutated (H61C, G644C and L65C, circled) or show ATP-dependent cross-linking (Met68 and Met69 , boxed) with residues in TM11 are shown as occupying one face of the helix.
X
ABCB1 p.His61Cys 16492138:215:70
status: NEW