ABCB1 p.Gly341Cys
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PMID: 10506575
[PubMed]
Loo TW et al: "The human multidrug resistance P-glycoprotein is inactive when its maturation is inhibited: potential for a role in cancer chemotherapy."
No.
Sentence
Comment
189
Some mutations such as G341C and Q347C (23, 46) expose a proteolytic site in the first extracellular loop that result in degradation of the protein during or immediately after synthesis.
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ABCB1 p.Gly341Cys 10506575:189:23
status: NEW205 The presence of mutations such as G341C (1); processing mutations (2); or the presence of proteasome inhibitors, such as MG-132 (3), prevent maturation of P-gp and the P-gps are rapidly degraded.
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ABCB1 p.Gly341Cys 10506575:205:34
status: NEW
PMID: 10585407
[PubMed]
Loo TW et al: "Identification of residues in the drug-binding domain of human P-glycoprotein. Analysis of transmembrane segment 11 by cysteine-scanning mutagenesis and inhibition by dibromobimane."
No.
Sentence
Comment
181
An example of an extreme case is mutant G341C (in TM6) that caused complete misfolding of P-gp such that the mutant P-gp was more susceptible to digestion in the first extracellular loop (50).
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ABCB1 p.Gly341Cys 10585407:181:40
status: NEW
PMID: 14670948
[PubMed]
Loo TW et al: "Disulfide cross-linking analysis shows that transmembrane segments 5 and 8 of human P-glycoprotein are close together on the cytoplasmic side of the membrane."
No.
Sentence
Comment
227
We had shown that mutations in TM6 such as G341C promoted proteolytic cleavage of P-gp between residues Arg-113 and Tyr-114 in ECL1 in the endoplasmic reticulum (62).
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ABCB1 p.Gly341Cys 14670948:227:43
status: NEW228 Mutant G341C was particularly sensitive to cleavage at R113 since no full-length protein was detected in cells expressing the mutant.
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ABCB1 p.Gly341Cys 14670948:228:7
status: NEW
PMID: 15192095
[PubMed]
Rothnie A et al: "The topography of transmembrane segment six is altered during the catalytic cycle of P-glycoprotein."
No.
Sentence
Comment
130
Values refer to the mean Ϯ S.E. obtained from at least eight independent protein purification preparations. P-gp isoform Substrate affinity , Km Maximal activity, Vmax -Fold stimulationBasal Stimulated Basal Stimulated mM mol Pi min-1 mg protein-1 Cys-less 0.58 Ϯ 0.06 0.38 Ϯ 0.04 0.58 Ϯ 0.15 1.46 Ϯ 0.30 2.9 Ϯ 0.3 V331C 0.50 Ϯ 0.06 0.26 Ϯ 0.02 0.45 Ϯ 0.05 1.54 Ϯ 0.20 3.5 Ϯ 0.3 T333C 0.49 Ϯ 0.05 0.23 Ϯ 0.02 0.35 Ϯ 0.04 1.22 Ϯ 0.15 3.3 Ϯ 0.1 F335C 0.40 Ϯ 0.05 0.24 Ϯ 0.03 0.65 Ϯ 0.15 1.61 Ϯ 0.31 2.2 Ϯ 0.2 S337C 0.53 Ϯ 0.06 0.26 Ϯ 0.04 0.59 Ϯ 0.10 1.67 Ϯ 0.23 3.2 Ϯ 0.4 L339C 0.51 Ϯ 0.07 0.31 Ϯ 0.04 0.57 Ϯ 0.07 1.47 Ϯ 0.15 2.9 Ϯ 0.3 G341C 0.40 Ϯ 0.04 0.24 Ϯ 0.02 0.42 Ϯ 0.03 1.12 Ϯ 0.09 3.1 Ϯ 0.5 F343C 0.41 Ϯ 0.04 0.26 Ϯ 0.03 0.47 Ϯ 0.04 1.17 Ϯ 0.15 2.6 Ϯ 0.3 generate stable covalent bonds with thiol groups under physiological conditions.
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ABCB1 p.Gly341Cys 15192095:130:829
status: NEW141 Typical time courses for labeling of T333C with FM and G341C with CM are shown in Fig 1, b and c, respectively.
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ABCB1 p.Gly341Cys 15192095:141:55
status: NEW147 Panel c clearly demonstrates that the labeling of G341C reached significantly higher levels (lanes i-vii) when compared with denatured protein (lane viii), which in this case indicates 100% labeling.
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ABCB1 p.Gly341Cys 15192095:147:50
status: NEW154 Isoforms V331C, T333C, F335C, S337C, L339C, and G341C displayed labeling extents in the range 7-12%, and none was significantly different from the Cys-less isoform (ANOVA).
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ABCB1 p.Gly341Cys 15192095:154:48
status: NEW163 Isoforms T333C, F335C, S337C, and G341C did not label with BM since the Lext values (19-27%) were not signif- TABLE II Potency of drugs that affect the ATPase activity of purified reconstituted single cysteine mutants of P-gp Pure, reconstituted P-gp (0.3 g) was incubated in the presence of ATP (2 mM) and varying concentrations of nicardipine, vinblastine, or vanadate.
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ABCB1 p.Gly341Cys 15192095:163:34
status: NEW166 Values refer to the mean Ϯ S.E. obtained from a minimum of three independent protein purification preparations. P-gp isoform Potency of drug effect Nicardipine, EC50 Vinblastine, EC50 Vanadate, IC50 M M M Cys-less 3.2 Ϯ 0.3 4.2 Ϯ 0.6 4.0 Ϯ 0.4 V331C 3.3 Ϯ 0.4 7.2 Ϯ 1.7 3.2 Ϯ 0.4 T333C 2.3 Ϯ 0.2 4.6 Ϯ 0.4 3.9 Ϯ 0.8 F335C 2.3 Ϯ 0.4 4.2 Ϯ 0.8 5.5 Ϯ 1.1 S337C 2.7 Ϯ 0.5 4.1 Ϯ 1.0 5.8 Ϯ 0.8 L339C 2.1 Ϯ 0.3 5.1 Ϯ 0.8 4.2 Ϯ 0.7 G341C 3.9 Ϯ 0.5 4.0 Ϯ 0.6 6.8 Ϯ 1.3 F343C 2.1 Ϯ 0.3 5.6 Ϯ 2.7 2.7 Ϯ 0.8 FIG. 1.
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ABCB1 p.Gly341Cys 15192095:166:562
status: NEW168 Structures of maleimide-containing probes (a) and the fluorescence profiles of SDS-PAGE gels obtained for time courses of fluorescein maleimide labeling of T333C (b) and coumarin maleimide labeling of G341C (c).
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ABCB1 p.Gly341Cys 15192095:168:201
status: NEW217 Two isoforms, F335C and G341C, could not be labeled by BM under any conditions and presumably lie in a region with low accessibility due to proximity of other structural elements.
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ABCB1 p.Gly341Cys 15192095:217:24
status: NEW
PMID: 15980350
[PubMed]
Harry JB et al: "Drug-induced regulation of the MDR1 promoter in Candida albicans."
No.
Sentence
Comment
115
When the promoters from each clone were sequenced, 13 MDR1 sequence differences were identified between the clones produced from isolates 1 and 17 (A306G, G341C, T343A, A448T, T565G, T655C, A682G, G724C, A739G, C755T, AAACAC811-816CC, A832C, and G890A, where the number refers to a position upstream of the ATG start codon based on the genome sequence [16], the base[s] before the number is the sequence from isolate 1, and the base[s] after the number is from isolate 17).
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ABCB1 p.Gly341Cys 15980350:115:155
status: NEW
PMID: 9405384
[PubMed]
Loo TW et al: "Identification of residues in the drug-binding site of human P-glycoprotein using a thiol-reactive substrate."
No.
Sentence
Comment
83
There was no detectable activity with mutants S344C, G341C, and G984C, whereas mutants A342C, G346C, Q347C, A985C, G989C, and Q990C had much reduced activity (10-40%).
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ABCB1 p.Gly341Cys 9405384:83:53
status: NEW87 Mutants G341C and G984C, however, appeared to be degraded quite rapidly.
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ABCB1 p.Gly341Cys 9405384:87:8
status: NEW96 Mutants G341C, S344C, G346C, G984C, and G989C were not assayed because of their low or defective expression (Fig. 2B).
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ABCB1 p.Gly341Cys 9405384:96:8
status: NEW
PMID: 9829963
[PubMed]
Loo TW et al: "Quality control by proteases in the endoplasmic reticulum. Removal of a protease-sensitive site enhances expression of human P-glycoprotein."
No.
Sentence
Comment
64
For some mutants such as G341C, no full-length protein could be detected.
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ABCB1 p.Gly341Cys 9829963:64:25
status: NEW67 To inhibit or retard the degradation of mutant G341C, synthesis was carried out in the presence of proteasome inhibitors such as MG-132 or lactacystin, because the major cellular degradation pathway is mediated by proteasomes (17).
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ABCB1 p.Gly341Cys 9829963:67:47
status: NEW68 Fig. 1 (lanes 8 and 9) shows that proteasomes are probably not involved because the 130-kDa protein was still the major product when mutant G341C was synthesized in the presence of proteasome inhibitors.
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ABCB1 p.Gly341Cys 9829963:68:140
status: NEW69 In contrast to mutant G341C, the proteasome inhibitors had a dramatic effect on synthesis of the Cys-less parent.
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ABCB1 p.Gly341Cys 9829963:69:22
status: NEW73 Therefore, the presence of a degradation product of 130 kDa in the Cys-less parent P-gp and in mutant G341C suggested that the protein had been cleaved at the NH2-terminal end.
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ABCB1 p.Gly341Cys 9829963:73:102
status: NEW93 HEK 293 cells were transfected with Cys-less (C-less), mutant G341C (in Cys-less background), or glycosylation-deficient (N91A,N94A,N99A; -Glycos.)
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ABCB1 p.Gly341Cys 9829963:93:62
status: NEW118 Mutant G341C appeared to have a greater folding defect than the G268V misprocessed mutant.
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ABCB1 p.Gly341Cys 9829963:118:7
status: NEW122 The R113A mutation was then introduced to block cleavage of the G341C mutant.
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ABCB1 p.Gly341Cys 9829963:122:64
status: NEW123 As shown in Fig. 5A (lane 3), the introduction of an R113A mutation significantly affected the synthesis of mutant G341C.
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ABCB1 p.Gly341Cys 9829963:123:115
status: NEW126 To determine whether the mature mutant protein was functional, the histidine-tagged mutant (G341C ϩ R113A) was expressed in HEK 293 cells and purified by nickel-chelate chromatography.
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ABCB1 p.Gly341Cys 9829963:126:92
status: NEW129 Mutant (G341C ϩ R113A) exhibited verapamiland vinblastine-stimulated ATPase activities that were similar to the parent enzyme.
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ABCB1 p.Gly341Cys 9829963:129:8
status: NEW130 These results show that blockage of the Arg113 cleavage site completely rescued the defects associated with the G341C mutation.
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ABCB1 p.Gly341Cys 9829963:130:112
status: NEW131 We could not determine whether the 130-kDa product of mutant G341C was active because the histidine-tagged protein was not retained by the nickel column, a property also exhibited by the core-glycosylated intermediates of other P-gp processing mutants (10).
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ABCB1 p.Gly341Cys 9829963:131:61
status: NEW132 The inability of the histidine-tagged 130-kDa product of mutant G341C to bind the nickel column was not due to loss of the histidine tag.
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ABCB1 p.Gly341Cys 9829963:132:64
status: NEW137 FIG. 5. Effect of R113A mutation on maturation and drug-stimulated ATPase activity of mutant G341C.
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ABCB1 p.Gly341Cys 9829963:137:93
status: NEW138 A, HEK 293 cells expressing P-gp-A52 mutants G341C or G341C ϩ R113A in Cys-less background were grown with (ϩ) or without (-) 10 M cyclosporin A for 24 h. Equivalent amounts of whole cell extracts were subjected to immunoblot analysis with monoclonal antibody A52.
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ABCB1 p.Gly341Cys 9829963:138:45
status: NEWX
ABCB1 p.Gly341Cys 9829963:138:54
status: NEW139 B, purified histidine-tagged Cys-less or mutant G341C ϩ R113A (in Cys-less background P-gp) were added to lipid and assayed for ATPase with or without verapamil (1 mM, shaded bars) or vinblastine (0.05 mM, unshaded bars).
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ABCB1 p.Gly341Cys 9829963:139:48
status: NEW146 This effect was enhanced in mutant G341C, such that the 130-kDa protein was the only product detected.
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ABCB1 p.Gly341Cys 9829963:146:35
status: NEW147 Remarkably, the effects of the G341C mutation could be overcome by mutating out the hypersensitive protease cleavage site.
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ABCB1 p.Gly341Cys 9829963:147:31
status: NEW148 Apparently, the G341C mutation does not cause complete misfolding of the protein because introduction of an additional R113A mutation to prevent degradation converts the mutant to a functional enzyme with characteristics indistinguishable from parent enzyme (Fig. 5B).
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ABCB1 p.Gly341Cys 9829963:148:16
status: NEW158 By inhibiting digestion at Arg113 , it was possible to increase expression of P-gp mutants such as G341C.
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ABCB1 p.Gly341Cys 9829963:158:99
status: NEW
PMID: 11557524
[PubMed]
Ito K et al: "Single amino acid substitution of rat MRP2 results in acquired transport activity for taurocholate."
No.
Sentence
Comment
223
Although we do not have a satisfactory explanation to account for the production of a shorter band of ϳ80 kDa in L1084RMRP3, it is possible this mutant protein may have easy access to some type of protease(s) that may be produced due to the Arg substitution at position 1084. Loo and Clarke (25) demonstrated that the substitution of Gly with Cys at position 341, located in the middle of the TM6 of P-glycoprotein, resulted in cleavage of the extracellular loop located between TM1 and TM2 to produce a truncated protein product of 130 kDa.
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ABCB1 p.Gly341Cys 11557524:223:340
status: NEW
No.
Sentence
Comment
315
Seven TM6 cysteine mutants (V331C, T333C, F335C, S337C, L339C, G341C, F343C) were labeled in the presence or absence of AMPÁPNP or after vanadate trapping of nucleotide.
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ABCB1 p.Gly341Cys 18328253:315:63
status: NEW313 Seven TM6 cysteine mutants (V331C, T333C, F335C, S337C, L339C, G341C, F343C) were labeled in the presence or absence of AMPPNP or after vanadate trapping of nucleotide.
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ABCB1 p.Gly341Cys 18328253:313:63
status: NEW
PMID: 23658020
[PubMed]
Wen PC et al: "On the origin of large flexibility of P-glycoprotein in the inward-facing state."
No.
Sentence
Comment
147
The suggested hinge role played by Gly-346 of human Pgp can also explain why the ATPase activity can only be significantly reduced by a mutation at this particular position but not elsewhere along the helix TM6 (73) even when other glycines in TM6 were targeted (G341C and G360C) (73).
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ABCB1 p.Gly341Cys 23658020:147:263
status: NEW