ABCG2 p.His583Ala
| Predicted by SNAP2: | A: D (59%), C: D (71%), D: D (75%), E: D (75%), F: D (75%), G: D (63%), I: D (53%), K: D (71%), L: D (63%), M: D (75%), N: D (66%), P: D (85%), Q: D (53%), R: D (66%), S: D (59%), T: D (59%), V: N (53%), W: D (80%), Y: N (53%), |
| Predicted by PROVEAN: | A: D, C: D, D: D, E: D, F: D, G: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: N, |
[switch to compact view]
Comments [show]
None has been submitted yet.
[hide] ABCG2 transports and transfers heme to albumin thr... J Biol Chem. 2010 Oct 22;285(43):33123-33. Epub 2010 Aug 12. Desuzinges-Mandon E, Arnaud O, Martinez L, Huche F, Di Pietro A, Falson P
ABCG2 transports and transfers heme to albumin through its large extracellular loop.
J Biol Chem. 2010 Oct 22;285(43):33123-33. Epub 2010 Aug 12., 2010-10-22 [PMID:20705604]
Abstract [show]
ABCG2 is an ATP-binding cassette (ABC) transporter preferentially expressed by immature human hematopoietic progenitors. Due to its role in drug resistance, its expression has been correlated with a protection role against protoporhyrin IX (PPIX) accumulation in stem cells under hypoxic conditions. We show here that zinc mesoporphyrin, a validated fluorescent heme analog, is transported by ABCG2. We also show that the ABCG2 large extracellular loop ECL3 constitutes a porphyrin-binding domain, which strongly interacts with heme, hemin, PPIX, ZnPPIX, CoPPIX, and much less efficiently with pheophorbide a, but not with vitamin B12. K(d) values are in the range 0.5-3.5 mum, with heme displaying the highest affinity. Nonporphyrin substrates of ABCG2, such as mitoxantrone, doxo/daunorubicin, and riboflavin, do not bind to ECL3. Single-point mutations H583A and C603A inside ECL3 prevent the binding of hemin but hardly affect that of iron-free PPIX. The extracellular location of ECL3 downstream from the transport sites suggests that, after membrane translocation, hemin is transferred to ECL3, which is strategically positioned to release the bound porphyrin to extracellular partners. We show here that human serum albumin could be one of these possible partners as it removes hemin bound to ECL3 and interacts with ABCG2, with a K(d) of about 3 mum.
Comments [show]
None has been submitted yet.
No. Sentence Comment
6 Single-point mutations H583A and C603A inside ECL3 prevent the binding of hemin but hardly affect that of iron-free PPIX.
X
ABCG2 p.His583Ala 20705604:6:23
status: VERIFIED220 Single-point Mutations H583A and C603A of ECL3 Alter Hemin Binding-We noticed that ECL3 displays a significant sequence similarity with the heme-binding domain of cytochrome b5, with 14.3% identity and 15.6% similarity, as shown in Fig. 6A.
X
ABCG2 p.His583Ala 20705604:220:23
status: VERIFIED224 As shown, the most striking differences were observed for hemin binding because the H583A and C603A mutations lowered the binding affinity 5-6-fold.
X
ABCG2 p.His583Ala 20705604:224:84
status: VERIFIED245 B, dissociation constants for hemin and PPIX binding to H583A, C603A, and Y605A mutant ECL3.
X
ABCG2 p.His583Ala 20705604:245:56
status: VERIFIED278 Heme and hemin appear to be the preferred ligands, because (i) they display the highest binding affinities for both the isolated ECL3 domain (0.5-1 M) and the full-length ABCG2 transporter (0.2 M); (ii) the H583A and C603A single-point mutations alter more markedly the binding of hemin than that of metal-free corresponding PPIX; and (iii) pheophorbide a, which is transported by ABCG2 (26), displays a low binding affinity for ECL3 (3 M), which is even lower for the full protein (Ͼ8 M) when saturated with MTX or doxorubicin, suggesting that pheophorbide a will not bind to ECL3 under physiological conditions.
X
ABCG2 p.His583Ala 20705604:278:223
status: VERIFIED