ABCMdb

ABCB1 p.Ile306Glu

Predicted by SNAP2:	A: D (63%), C: D (53%), D: D (85%), E: D (85%), F: N (53%), G: D (75%), H: D (80%), K: D (85%), L: D (63%), M: N (82%), N: D (71%), P: D (85%), Q: D (80%), R: D (85%), S: D (66%), T: D (63%), V: N (72%), W: D (85%), Y: D (80%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, 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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Publications
[hide] The drug-binding pocket of the human multidrug res... Biochemistry. 2004 Sep 28;43(38):12081-9. Loo TW, Bartlett MC, Clarke DM
The drug-binding pocket of the human multidrug resistance P-glycoprotein is accessible to the aqueous medium.
Biochemistry. 2004 Sep 28;43(38):12081-9., 2004-09-28 [PMID:15379547]

Abstract [show]
P-Glycoprotein (P-gp) is an ATP-dependent drug pump that transports a broad range of compounds out of the cell. Cross-linking studies have shown that the drug-binding pocket is at the interface between the transmembrane (TM) domains and can simultaneously bind two different drug substrates. Here, we determined whether cysteine residues within the drug-binding pocket were accessible to the aqueous medium. Cysteine mutants were tested for their reactivity with the charged thiol-reactive compounds sodium (2-sulfonatoethyl)methanethiosulfonate (MTSES) and [2-(trimethylammonium)ethyl)]methanethiosulfonate (MTSET). Residue Ile-306(TM5) is close to the verapamil-binding site. It was changed to cysteine, reacted with MTSES or MTSET, and assayed for verapamil-stimulated ATPase activity. Reaction of mutant I306C(TM5) with either compound reduced its affinity for verapamil. We confirmed that the reduced affinity for verapamil was indeed due to introduction of a charge at position 306 by demonstrating that similar effects were observed when Ile-306 was replaced with arginine or glutamic acid. Mutant I306R showed a 50-fold reduction in affinity for verapamil and very little change in the affinity for rhodamine B or colchicine. MTSES or MTSET modification also affected the cross-linking pattern between pairs of cysteines in the drug-binding pocket. For example, both MTSES and MTSET inhibited cross-linking between I306C(TM5) and I868C(TM10). Inhibition was enhanced by ATP hydrolysis. By contrast, cross-linking of cysteine residues located outside the drug-binding pocket (such as G300C(TM5)/F770C(TM8)) was not affected by MTSES or MTSET. These results indicate that the drug-binding pocket is accessible to water.

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No. Sentence Comment
48 Histidine-tagged wild-type P-gp and mutants I306E and I306R were constructed as described previously (35, 36). Login to comment
113 Therefore, an alternative approach to introduce a charged group at position 306 would be to mutate Ile306 to glutamic acid or arginine. Login to comment
123 Histidine-tagged wild-type and mutants I306E and I306R P-gps were expressed in HEK 293 cells, isolated by nickel-chelate chromatography and mixed with lipid, and verapamil-stimulated ATPase activity was determined. Login to comment
124 Figure 4 shows that mutation of Ile306 to glutamic acid or arginine significantly affected the apparent affinity for verapamil. Login to comment
125 The wild-type P-gp and mutants I306R and I306E showed maximal stimulation of 16.1-, >10.8-, and 7-fold and S50 (concentration required for 50% stimulation) of 44, >2200, and 305 µM, respectively. Login to comment
139 HEK 293 cells were transfected with wild-type P-gp or with P-gp mutants I306E or I306R (in wild-type background) cDNAs. After 24 h, the medium was replaced with fresh medium. Login to comment
143 FIGURE 4: Verapamil-stimulated ATPase activity of wild-type and mutant I306R and I306E P-gps. Login to comment
144 Histidine-tagged wild-type, mutant I306R or mutant I306E P-gps were expressed in HEK 293 cells and isolated by nickel-chelate chromatography. Login to comment