ABCB6 p.Cys50Ala
| Predicted by SNAP2: | A: N (82%), D: D (53%), E: N (57%), F: N (82%), G: N (72%), H: N (78%), I: N (87%), K: N (57%), L: N (87%), M: N (93%), N: N (66%), P: D (53%), Q: N (66%), R: N (61%), S: N (72%), T: N (78%), V: N (87%), W: N (78%), Y: N (78%), |
| Predicted by PROVEAN: | A: N, D: N, E: N, F: N, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, R: N, S: N, T: N, V: N, W: N, Y: N, |
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[hide] Conserved intramolecular disulfide bond is critica... J Biol Chem. 2011 Mar 11;286(10):8481-92. Epub 2011 Jan 3. Fukuda Y, Aguilar-Bryan L, Vaxillaire M, Dechaume A, Wang Y, Dean M, Moitra K, Bryan J, Schuetz JD
Conserved intramolecular disulfide bond is critical to trafficking and fate of ATP-binding cassette (ABC) transporters ABCB6 and sulfonylurea receptor 1 (SUR1)/ABCC8.
J Biol Chem. 2011 Mar 11;286(10):8481-92. Epub 2011 Jan 3., [PMID:21199866]
Abstract [show]
The ATP-binding cassette (ABC) transporter ABCB6 is a mitochondrial porphyrin transporter that activates porphyrin biosynthesis. ABCB6 lacks a canonical mitochondrial targeting sequence but reportedly traffics to other cellular compartments such as the plasma membrane. How ABCB6 reaches these destinations is unknown. In this study, we show that endogenous ABCB6 is glycosylated in multiple cell types, indicating trafficking through the endoplasmic reticulum (ER), and has only one atypical site for glycosylation (NXC) in its amino terminus. ABCB6 remained glycosylated when the highly conserved cysteine (Cys-8) was substituted with serine to make a consensus site, NXS. However, this substitution blocked ER exit and produced ABCB6 degradation, which was mostly reversed by the proteasomal inhibitor MG132. The amino terminus of ABCB6 has an additional highly conserved ER luminal cysteine (Cys-26). When Cys-26 was mutated alone or in combination with Cys-8, it also resulted in instability and ER retention. Further analysis revealed that these two cysteines form a disulfide bond. We discovered that other ABC transporters with an amino terminus in the ER had similarly configured conserved cysteines. This analysis led to the discovery of a disease-causing mutation in the sulfonylurea receptor 1 (SUR1)/ABCC8 from a patient with hyperinsulinemic hypoglycemia. The mutant allele only contains a mutation in a conserved amino-terminal cysteine, producing SUR1 that fails to reach the cell surface. These results suggest that for ABC transporters the propensity to form a disulfide bond in the ER defines a unique checkpoint that determines whether a protein is ER-retained.
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No. Sentence Comment
61 The region encoding the amino-terminal 210 amino acids was then amplified with a FLAG tag at the carboxyl terminus from pcDNA3.1-hABCB6-C50A/C120A-V5 or pcDNA3.1-hABCB6-C8S/C50A/C120A-V5 by using primers (sense, 5Ј-GCCATGGTGACTGTGGGCAACTACTG- CGAGGCCG-3Ј; antisense, 5Ј-CCTACTTATCGTCGTCATC- CTTGTAATCACGAAGTCCAGGGGCCCAGAG-3Ј) under the following conditions: heating at 94 °C for 4 min, 30 cycles of denaturation at 94 °C for 30 s, annealing at 56 °C for 30 s, and reaction at 68 °C for 1 min.
X
ABCB6 p.Cys50Ala 21199866:61:136
status: NEWX
ABCB6 p.Cys50Ala 21199866:61:173
status: NEW63 The inserts were subcloned into pcDNA3 using HindIII/XbaI sites to obtain pcDNA3.1- hABCB6-C50A/C120AN1-210-FLAG or pcDNA3.1-hABCB6-C8S/C50A/C120AN1-210-FLAG constructs.
X
ABCB6 p.Cys50Ala 21199866:63:91
status: NEWX
ABCB6 p.Cys50Ala 21199866:63:136
status: NEW217 To rule out the contribution of the two additional cysteines (Cys-120 and Cys-150) present in this segment, we then developed a chimeric expression plasmid encoding the amino-terminal 210 amino acids of ABCB6 fused to a carboxyl-terminal FLAG epitope where both Cys-120 and Cys-150 were substituted with Ala (ABCB6-C50A/C120AN1-210-FLAG).
X
ABCB6 p.Cys50Ala 21199866:217:315
status: NEW220 We next compared the electrophoretic migration of ABCB6-C50A/C120AN1-210-FLAG and the cysteine mutant ABCB6-C8S/C50A/C120AN1-210-FLAG in the presence versus absence of the reducing agent DTT (Fig. 6B).
X
ABCB6 p.Cys50Ala 21199866:220:56
status: NEWX
ABCB6 p.Cys50Ala 21199866:220:112
status: NEW223 ABCB6-C50A/ C120AN1-210-FLAG exhibited three faster migrating bands in the absence of DTT (Fig. 6B).
X
ABCB6 p.Cys50Ala 21199866:223:6
status: NEW257 B, ABCB6-C50A/C120AN1-210-FLAG and ABCB6-C8S/C50A/C120AN1-210-FLAG were expressed in NIH3T3 cells, treated with N-ethylmaleimide to prevent spontaneous disulfide bonds, separated by SDS-PAGE with or without DTT, and analyzed by immunoblotting.
X
ABCB6 p.Cys50Ala 21199866:257:9
status: NEWX
ABCB6 p.Cys50Ala 21199866:257:45
status: NEW