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Title: PROTEIN TRANSLOCATION SYSTEMS IN MOLLICUTES: PREDICTED SECRETOME OF THE PLANT PATHOGENIC BACTERIUM SPIROPLASMA KUNKELII

Author
item Zhao, Yan
item LIU, QINGZHONG - SHANGDONG CHINA
item JOMANTIENE, RASA - VILNIUS LITHUANIA
item Hammond, Rosemarie
item Davis, Robert

Submitted to: International Organization for Mycoplasmology
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2004
Publication Date: 7/11/2004
Citation: Zhao, Y., Liu, Q., Jomantiene, R., Hammond, R., Davis, R.E. 2004. Protein translocation systems in mollicutes: predicted secretome of the plant pathogenic bacterium spiroplasma kunkelii. International Organization for Mycoplasmology. p. 139-140.

Interpretive Summary:

Technical Abstract: Spiroplasmas are helical and motile bacteria that lack a rigid cell wall. The first recognized was the helically shaped mycoplasma-like organism associated with corn stunt diseased maize. For this unique group of prokaryotes, the term 'spiroplasma' was coined. Spiroplasmas parasitize insects and ticks; some are pathogenic to plants. Under experimental conditions, certain spiroplasmas induce pathology in vertebrate animals and some have been linked to human diseases. Although spiroplasmal diseases impact agriculture and human health, little is known about the fundamental biology or mechanisms of pathogenesis of these micro-parasites. Spiroplasmas are thought to have evolved retrogressively from low G+C gram-positive bacteria and, as a result, to possess a compact genome with a gene set approaching the minimal complement necessary for cellular life and pathogenesis. As the corn stunt spiroplasma genome-sequencing project comes to near completion, we started to assemble the metabolic pathways and functional systems that operate in the pathogen. The present study focused on the secreted and membrane-localized proteins and protein translocation systems encoded by the Spiroplasma kunkelii genome. A total of 258 predicted proteins contained N-terminal signal peptides and/or membrane sorting signals. Genes encoding these preproteins occupy 18% of the coding capacity of the S. kunkelii genome. Based on the presence of genes encoding components of protein transport machineries and/or of signature motifs embedded in the signal peptides of transported preproteins, we predict the existence in S. kunkelii of multiple protein translocation pathways. These include a Sec-dependent secretion pathway, a type IV secretion pathway, a twin arginine pathway, a signal recognition particle-dependent pathway, and an ABC transporter-mediated pathway. Since protein translocation is a major determinant in microbial biology, including pathogenesis and virulence, the discovery of multiple secretion pathways in S. kunkelii opens new opportunities for understanding their functional roles in numerous biological processes of spiroplasmas.