ABCG2

The membrane-associated protein encoded by this gene is included in the superfamily of ATP-binding cassette (ABC) transporters. ABC proteins transport various molecules across extra- and intra-cellular membranes. ABC genes are divided into seven distinct subfamilies (ABC1, MDR/TAP, MRP, ALD, OABP, GCN20, White). This protein is a member of the White subfamily. Alternatively referred to as a breast cancer resistance protein, this protein functions as a xenobiotic transporter which may play a major role in multi-drug resistance. It likely serves as a cellular defense mechanism in response to mitoxantrone and anthracycline exposure. Significant expression of this protein has been observed in the placenta, which may suggest a potential role for this molecule in placenta tissue. [provided by RefSeq]

ATP-binding cassette, sub-family G (WHITE), member 2

Broad substrate specificity ATP-dependent transporter of the ATP-binding cassette (ABC) family that actively extrudes a wide variety of physiological compounds, dietary toxins and xenobiotics from cells. Involved in porphyrin homeostasis, mediating the export of protoporphyrin IX (PPIX) from both mitochondria to cytosol and cytosol to extracellular space, it also functions in the cellular export of heme. Also mediates the efflux of sphingosine-1-P from cells. Acts as a urate exporter functioning in both renal and extrarenal urate excretion. In kidney, it also functions as a physiological exporter of the uremic toxin indoxyl sulfate (By similarity). Also involved in the excretion of steroids like estrone 3-sulfate/E1S, 3beta-sulfooxy-androst-5-en-17-one/DHEAS, and other sulfate conjugates. Mediates the secretion of the riboflavin and biotin vitamins into milk (By similarity). Extrudes pheophorbide a, a phototoxic porphyrin catabolite of chlorophyll, reducing its bioavailability (By similarity). Plays an important role in the exclusion of xenobiotics from the brain (Probable). It confers to cells a resistance to multiple drugs and other xenobiotics including mitoxantrone, pheophorbide, camptothecin, methotrexate, azidothymidine, and the anthracyclines daunorubicin and doxorubicin, through the control of their efflux. In placenta, it limits the penetration of drugs from the maternal plasma into the fetus (By similarity). May play a role in early stem cell self-renewal by blocking differentiation (By similarity).

Biotin transport
Cellular detoxification
Cellular iron ion homeostasis
Export across plasma membrane
Heme biosynthetic process
Heme catabolic process
Organic anion transport
Riboflavin transport
Transepithelial transport
Transmembrane transport
Transport across blood-brain barrier
Urate metabolic process
Urate salt excretion
Xenobiotic transport across blood-brain barrier

Cell membrane; Apical cell membrane; Mitochondrion membrane. Enriched in membrane lipid rafts.

Cytoplasmic: 1-395 aa
Helical: 396-416 aa
Extracellular: 417-428 aa
Helical: 429-449 aa
Cytoplasmic: 450-477 aa
Helical: 478-498 aa
Extracellular: 499-506 aa
Helical: 507-527 aa
Cytoplasmic: 528-535 aa
Helical: 536-556 aa
Extracellular: 557-630 aa
Helical: 631-651 aa
Cytoplasmic: 652-655 aa

N-glycosylated. Glycosylation-deficient ABCG2 is normally expressed and functional.
Phosphorylated. Phosphorylation at Thr-362 by PIM1 is induced by drugs like mitoxantrone and is associated with cells increased drug resistance. It regulates the localization to the plasma membrane, the homooligomerization and therefore, the activity of the transporter.