title: Ligand heterogeneity of the cysteine protease binding protein family in the parasitic protist Entamoeba histolytica.
abstract: Lysosomal soluble proteins are targeted to endosomes and lysosomes by specific receptors resident in the endoplasmic reticulum and/or the Golgi apparatus. The enteric protozoan parasite Entamoeba histolytica has a novel class of lysosomal targeting receptors, named the cysteine protease binding protein family (CPBF). Among 11 CPBFs (CPBF1-11), ligands for three members, CPBF1, CPBF6 and CPBF8, were previously shown to be cysteine proteases, α- and γ- amylases, and β-hexosaminidase and lysozymes, respectively. To further understand the heterogeneity of the ligands of CPBFs, we attempted to isolate and identify the ligands for other members of CPBFs, namely CPBF2, 3, 4, 5, 7, 9, 10 and 11, by immunoprecipitation and mass spectrometric analysis. We found that CPBF2 and CPBF10 bound to α-amylases while CPBF7 bound to β-hexosaminidases. It is intriguing that cysteine protease are exclusively recognised by CPBF1, whereas three α-amylases and β-hexosaminidases are redundantly recognised by three and two CPBFs, respectively. It was shown by bioinformatics analysis and phylogenetic reconstruction that each CPBF contains six prepeptidase carboxyl-terminal domains, and the domain configuration is evolutionarily conserved among CPBFs. Taken together, CPBFs with unique and conserved domain organisation have a remarkable ligand heterogeneity toward cysteine protease and carbohydrate degradation enzymes. Further structural studies are needed to elucidate the structural basis of the ligand specificity.
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Konomi
authors.initials: K
authors.lastname: Marumo
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Nakada-Tsukui
authors.affiliation: Computational Biology Research Center (CBRC), National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo 135-0064, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Tomii
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan. Electronic address: nozaki@nih.go.jp.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Nozaki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D057056:Cysteine Proteases / Q000378:metabolism*; D004748:Entamoeba histolytica / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D047468:Immunoprecipitation; D008024:Ligands; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011485:Protein Binding
chemical_list: D008024:Ligands; D057056:Cysteine Proteases
keywords: Amylase; Cysteine protease; Entamoeba histolytica; Lysosomes; Receptor; β-Hexosaminidase