title: Characterization of a subtilisin-like protease with apical localization from microsporidian Nosema bombycis.
abstract: The microsporidian Nosema bombycis is the pathogen causing pébrine leading to heavy economic loss in sericulture. Little is known of the proteases of microsporidia that are important for both parasite development and pathogenesis. Here we identified a subtilisin-like serine protease NbSLP1 which contains an inhibitor_I9 and a peptidase_S8 domain. Three dimensional modeling of the catalytic domain of the NbSLP1 exhibited a typical 3-layer sandwich structure with S1 pocket substituted by Y(359). Phylogenetic analysis confirms that subtilisin-like serine proteases of microsporidia fall into two clades: SLP1 and SLP2, suggesting the initial subtilisin gene duplication events preceded microsporidia speciation. Furthermore, transcripts of Nbslp1 were detected in the midgut of Bombyx mori infection by N. bombycis by RT-PCR. Antibodies against NbSLP1 recognized both the precursor and mature enzyme by 2D Western blotting. Besides, indirect immunofluorescence assay revealed that the NbSLP1 is mainly localized at the two poles of spore which make the spore look like "safety pins". Remarkably, the mature protease is only detected in the apical region of the spore after germination. These studies demonstrate that NbSLP1 is a conserved subtilisin protease in microsporidia and suggest that NbSLP1 play a significant role in polar tube extrusion process.
authors.affiliation: The State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Beibei, Chongqing 400716, People's Republic of China.
authors.forename: Xiaoqun
authors.initials: X
authors.lastname: Dang
authors.forename: Guoqing
authors.initials: G
authors.lastname: Pan
authors.forename: Tian
authors.initials: T
authors.lastname: Li
authors.forename: Lipeng
authors.initials: L
authors.lastname: Lin
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ma
authors.forename: Lina
authors.initials: L
authors.lastname: Geng
authors.forename: Yuanli
authors.initials: Y
authors.lastname: He
authors.forename: Zeyang
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000818:Animals; D012831:Bombyx / Q000382:microbiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000382:microbiology; D008969:Molecular Sequence Data; D016818:Nosema / Q000201:enzymology* / Q000502:physiology; D010572:Pest Control, Biological; D057057:Serine Proteases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013170:Spores; D020860:Subtilisin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D057057:Serine Proteases; D020860:Subtilisin