ペルオキシソームABCタンパク質と脂肪酸代謝
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概要
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ATP-binding cassette (ABC) superfamily proteins are composed of two homologous halves, each half containing a transmembrane domain (TMD) and a nucleotide-binding domain (NBD). They catalyze the ATP-dependent trans-membrane translocation of a wide variety of substrate including several kinds of lipids. Peroxisomes are organelles bounded by a single membrane and are involved in a variety metabolic process including oxidative degradation of fatty acids. To date, four ABC proteins have been identified in mammalian peroxisomes. The 70-kDa peroxisomal membrane protein (PMP70, ABCD3) is suggested to be involved in ATP-dependent transport of long chain acyl-CoA into peroxisomes. Adrenoleukodystrophy protein (ALDP, ABCD1) seems to be involved in metabolism of very long chain fatty acids. This defect is known to be responsible for the X-linked neurodegeneration disorder adrenoleukodystrophy (ALD). Other two proteins are ALD-related protein (ALDRP, ABCD2) and PMP70-related protein (P7OR, ABCD4). Peroxisomal ABC proteins are synthesized on free polysosmes and inserted post-translationally into peroxisomal membranes. Pex19p, a chaperone-like protein, plays an important role in the targeting of peroxisomal ABC proteins. As peroxisomal ABC proteins are half size, they seem to function as homo- and heterodimer on peroxisomal membranes. Recently, PMP70 was shown to change its conformations at the region between TMD and NBD, and the helical domain between Walker A and B motifs during the cycle of the binding and hydrolysis of ATP. The conformational changes seem to be important to transport the substrate.
- 2003-11-01