Abstract
The 70-kDa peroxisomal membrane protein (PMP70) is one of the major integral membrane proteins of rat liver peroxisomes. cDNA clones for PMP70 were isolated and sequenced. The predicted amino acid sequence (659 amino acid residues) revealed that the carboxyl-terminal region of PMP70 has strong sequence similarities to a group of ATP-binding proteins such as MalK and Mdr. These proteins form a superfamily and are involved in various biological processes including membrane transport. Limited protease treatment of peroxisomes showed that the ATP-binding domain of PMP70 is exposed to the cytosol. The hydropathy profile, in comparison with those of several other members of the ATP-binding protein superfamily, suggests that PMP70 is a transmembrane protein possibly forming a channel. Based on these results, we propose that PMP70 is involved in active transport across the peroxisomal membrane.
Highlights
From the *Department of Biockemis@, Shinshu University School of Medicine, Matsunwto 390, Japan, the §Department of Hygiene, Kansai Medical School, Moriguchi 570, Japan, and the llDepurtment of Anatomy, Yamanashi Medic&l S&01, Yamanushi 409-38, Japan
We propose that PMP70 is involved in active transport across the peroxisomal membrane
Iso&ion of cDNA Clones-Poly(A) RNA was purified from the liver of a rat treated with gel electrophoresis (DEHP), an inducing agent of PMP70 mRNA [14]. cDNA was synthesized from the poly(A) RNA preparation, and libraries were constructed in QtlO and Q$ll
Summary
From the *Department of Biockemis@, Shinshu University School of Medicine, Matsunwto 390, Japan, the §Department of Hygiene, Kansai Medical School, Moriguchi 570, Japan, and the llDepurtment of Anatomy, Yamanashi Medic&l S&01, Yamanushi 409-38, Japan. The hydropathy profile, in comparison with those of several other members of the ATP-binding protein superfamily, suggests that PMP70 is a transmembrane protein possibly forming a channel. Based on these results, we propose that PMP70 is involved in active transport across the peroxisomal membrane. The physiological significance of peroxisomes has remained elusive, diseases caused by a dysfunction of peroxisomes, including Zellweger syndrome, have recently been recognized (for review, see Ref. 1). Biogenesis of peroxisomes is apparently impaired in this disorder; the cause may be defects in the protein import machinery of the peroxisomes [3]. Peroxisome-targeting signal sequences have been characterized by in uitro and in viuo import assays using recombinant
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