A novel Mitosomal β-barrel Outer Membrane Protein in Entamoeba.

Herbert J Santos, Kenichiro Imai, Takashi Makiuchi, Kentaro Tomii, Paul Horton, Akira Nozawa, Mohamed Ibrahim, Yuzuru Tozawa, Tomoyoshi Nozaki

Journal: Scientific reports 2015;5():8545

PMID: 25711150

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Abstract

Entamoeba possesses a highly divergent mitochondrion-related organelle known as the mitosome. Here, we report the discovery of a novel protein in Entamoeba, which we name Mitosomal β-barrel Outer Membrane Protein of 30 kDa (MBOMP30). Initially identified through in silico analysis, we experimentally confirmed that MBOMP30 is indeed a β-barrel protein. Circular dichroism analysis showed MBOMP30 has a predominant β-sheet structure. Localization to Entamoeba histolytica mitosomes was observed through Percoll-gradient fractionation and immunofluorescence assay. Mitosomal membrane integration was demonstrated by carbonate fractionation, proteinase K digestion, and immunoelectron microscopy. Interestingly, the deletion of the putative β-signal, a sequence believed to guide β-barrel outer membrane protein (BOMP) assembly, did not affect membrane integration, but abolished the formation of a ~240 kDa complex. MBOMP30 represents only the seventh subclass of eukaryotic BOMPs discovered to date and lacks detectable homologs outside Entamoeba, suggesting that it may be unique to Entamoeba mitosomes.

Address: 1] Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan [2] Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan [3] Institute of Biology, College of Science, University of the Philippines Diliman, Quezon City, 1101 Philippines.; Computational Biology Research Center (CBRC), National Institute of Advanced Industrial Science and Technology (AIST), 2-4-7 Aomi, Koto-ku, Tokyo 135-0064, Japan.; Department of Infectious Diseases, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan.; Proteo-Science Center, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.; Botany Department, Faculty of Science, Ain Shams University, Khalifa El-Maamon St, Abbasiya Sq., Cairo, 11566, Egypt.; Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, Saitama 338-8570, Japan.; 1] Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan [2] Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.

DOI: 10.1038/srep08545

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MeSH Terms: Amino Acid Sequence, Circular Dichroism, Entamoeba histolytica, Immunoprecipitation, Membrane Proteins, Microscopy, Immunoelectron, Mitochondria, Molecular Sequence Data, Sequence Alignment, Sequence Homology, Amino Acid, Spectrophotometry, Ultraviolet