title: The protein import pore Tom40 in the microsporidian Nosema bombycis.
abstract: Microsporidia, an unusual group of unicellular parasites related to fungi, possess a highly reduced mitochondrion known as the mitosome. Since mitosomes lack an organellar genome, their proteins must be translated in the cytosol before being imported into the mitosome via translocases. We have identified a Tom40 gene (NbTom40), the main component of the translocase of the outer mitochondrial membrane, in the genome of the microsporidian Nosema bombycis. NbTom40 is reduced in size, but it is predicted to form a β-barrel structure composed of 19 β-strands. Phylogenetic analysis confirms that NbTom40 forms a clade with Tom40 sequences from other species, distinct from a related clade of voltage-dependent anion channels (VDACs). The NbTom40 contains a β-signal motif that the polar residue is substituted by glycine. Furthermore, we show that expression of NbTom40, as a GFP fusion protein within yeast cells, directs GFP to mitochondria of yeast. These findings suggest that NbTom40 may serve as an import channel of the microsporidian mitosome and facilitate protein translocation into this organelle.
authors.affiliation: The State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Lipeng
authors.initials: L
authors.lastname: Lin
authors.forename: Guoqing
authors.initials: G
authors.lastname: Pan
authors.forename: Tian
authors.initials: T
authors.lastname: Li
authors.forename: Xiaoqun
authors.initials: X
authors.lastname: Dang
authors.forename: Yuanhong
authors.initials: Y
authors.lastname: Deng
authors.forename: Cheng
authors.initials: C
authors.lastname: Ma
authors.forename: Jie
authors.initials: J
authors.lastname: Chen
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.forename: Zeyang
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D019295:Computational Biology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016814:Microsporidia / Q000145:classification / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D016818:Nosema / Q000145:classification / Q000378:metabolism*; D010802:Phylogeny; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D033681:Mitochondrial Membrane Transport Proteins