ABCG subfamily of human ATP-binding cassette proteins
S. Lorkowski1,* and P. Cullen1,2
1 Institut für Arterioskleroseforschung, Domagkstraße
3, D-48149 Münster, Germany;
2 Ogham GmbH, Mendelstraße 11, D-48149 Münster, Germany
Abstract: ATP-binding cassette (ABC) proteins form one of the
largest known protein families and have been found in all known organisms.
Most members of the human ABC protein family are membrane-spanning transporters
that use energy derived from the hydrolysis of ATP to transport specific
substrates across cell membranes. Mutations in certain human ABC transporters
of the subfamilies A, B, C, and D have been shown to cause a wide variety
of inherited diseases such as the lung condition cystic fibrosis, the
nervous degenerative condition adrenoleukodystrophy (of Lorenzos
Oil fame), hereditary macular degeneration of the eye (Stargardts
disease), and inherited deficiency of circulating high-density lipoproteins
(Tangier disease or familial hypoalphalipoproteinemia). Very recent
studies showed that mutations in two members of the subfamily G of human
ABC transporters (ABCG5 and ABCG8) cause a condition called sitosterolemia
in which plant sterols accumulate in the body and may be responsible
for influencing total body sterol homeostasis. In addition, other members
of the subfamily G, namely ABCG1 and ABCG4, have also been shown to
be involved in cellular lipid trafficking and are thought to play important
roles during foam cell formation of human macrophages. By contrast,
ABCG2 is a multidrug resistance transporter.
In this review, we focus on the current knowledge and physiological
background of the members of the subfamily G. We also present new insights
on the evolutionary relationship of human and nonhuman ABCG proteins.
* Pure Appl. Chem.
74, 2021-2081 (2002). A collection of invited, peer-reviewed articles
by the winners of the 2002 IUPAC Prize for Young Chemists.
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