Targeting elements in the amino-terminal part direct the human 70-kDa peroxisomal integral membrane protein (PMP70) to peroxisomes

Peroxisomes are multipurpose organelles present in nearly all eukaryotic ce lls. All peroxisomale matrix and membrane proteins are synthesized in the c ytoplasm. While a clear picture of the basic targeting mechanisms for perox isomal matrix proteins has emerged over the past years, the targeting proce sses for peroxisomal membrane proteins are poorly understood. The 70-kDa pe roxisomal integral membrane protein (PMP70) is one of the proteins located in the human peroxisome membrane. PMP70 belongs; to the family of ATP-bindi ng cassette (ABC) transporter proteins. It consists of six transmembrane do mains and an ATP-binding fold in the cytosol. Here we describe that efficie nt peroxisomal targeting of human PMP70 depends on three targeting elements in the aminoterminal protein region, namely amino acids 61 to 80 located i n the cytosol as well as the first and second transmembrane domains. Furthe rmore, peroxin 19 (PEX19) interactions are not required for targeting human PMP70 to peroxisomes. PEX19 does not specifically bind to the targeting el ements of human PMP70. (C) 2001 Academic Press.