ABCMdb

ABCB1 p.Asn428Cys

Predicted by SNAP2:	A: N (87%), C: D (66%), D: N (78%), E: N (87%), F: D (75%), G: N (82%), H: N (82%), I: N (57%), K: N (78%), L: N (57%), M: N (78%), P: N (78%), Q: N (93%), R: N (61%), S: N (97%), T: N (93%), V: N (61%), W: D (80%), Y: D (75%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, G: N, H: N, I: D, K: N, L: D, M: D, P: D, Q: N, R: N, S: N, T: N, V: D, W: D, Y: D,

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Publications
[hide] The "LSGGQ" motif in each nucleotide-binding domai... J Biol Chem. 2002 Nov 1;277(44):41303-6. Epub 2002 Sep 10. Loo TW, Bartlett MC, Clarke DM
The "LSGGQ" motif in each nucleotide-binding domain of human P-glycoprotein is adjacent to the opposing walker A sequence.
J Biol Chem. 2002 Nov 1;277(44):41303-6. Epub 2002 Sep 10., 2002-11-01 [PMID:12226074]

Abstract [show]
The human multidrug resistance P-glycoprotein (P-gp, ABCB1), a member of the ATP-binding cassette (ABC) family of transport proteins, actively transports many cytotoxic compounds out of the cell. ABC transporters have two nucleotide-binding domains (NBD) and two transmembrane domains. The presence of the conserved "signature" sequence (LSGGQ) in each NBD is a unique feature in these transporters. The function of the signature sequences is unknown. In this study, we tested whether the signature sequences ((531)LSGGQ(535) in NBD1; (1176)LSGGQ(1180) in NBD2) in P-gp are in close proximity to the opposing Walker A consensus nucleotide-binding sequences ((1070)GSSGCGKS(1077) in NBD2; (427)GNSGCGKS(434) in NBD1). Pairs of cysteines were introduced into a Cys-less P-gp at the signature and "Walker A" sites and the mutant P-gps were subjected to oxidative cross-linking. At 4 degrees C, when thermal motion is low, P-gp mutants (L531C(Signature)/C1074(Walker A) and C431(Walker A)/L1176C(Signature) were cross-linked. Cross-linking inhibited the drug-stimulated ATPase activities of these two mutants. Their activities were restored, however, after addition of the reducing agent, dithiothreitol. Vanadate trapping of nucleotide at the ATP-binding sites prevented cross-linking of the mutants. These results indicate that the signature sequences are adjacent to the opposing Walker A site. They likely participate in forming the ATP-binding sites and are displaced upon ATP hydrolysis. The resulting conformational change may be the signal responsible for coupling ATP hydrolysis to drug transport by inducing conformational changes in the transmembrane segments.

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No. Sentence Comment
77 Cross-linking involving residues G427C, N428C, and S434C was not done because the single cysteine mutants, G427C and S434C, showed little or no activity (Ͻ5%), while N428C was defectively processed and rapidly degraded. Login to comment