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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: M900012-MCP200v1 8/11/2570    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Glossary Google Scholar Articles by Palmieri, G. Articles by Pocsfalvi, G. PubMed PubMed Citation Articles by Palmieri, G. Articles by Pocsfalvi, G. Social Bookmarking                      What's this?

Molecular & Cellular Proteomics 8:2570-2581, 2009.
© 2009 by The American Society for Biochemistry and Molecular Biology, Inc.

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Research

Outside the Unusual Cell Wall of the Hyperthermophilic Archaeon Aeropyrum pernix K1

Gianna Palmieri, Raffaele Cannio, Immacolata Fiume, Mosé Rossi and Gabriella Pocsfalvi^,¶

From the Institute of Protein Biochemistry-National Research Council, 80131 Naples and
Department of Structural and Functional Biology, University of Naples Federico II, 80134 Naples, Italy

In contrast to the extensively studied eukaryal and bacterial protein secretion systems, comparatively less is known about how and which proteins cross the archaeal cell membrane. To identify secreted proteins of the hyperthermophilic archaeon Aeropyrum pernix K1 we used a proteomics approach to analyze the extracellular and cell surface protein fractions. The experimentally obtained data comprising 107 proteins were compared with the in silico predicted secretome. Because of the lack of signal peptide and cellular localization prediction tools specific for archaeal species, programs trained on eukaryotic and/or Gram-positive and Gram-negative bacterial signal peptide data sets were used. PSortB Gram-negative and Gram-positive analysis predicted 21 (1.2% of total ORFs) and 24 (1.4% of total ORFs) secreted proteins, respectively, from the entire A. pernix K1 proteome, 12 of which were experimentally identified in this work. Six additional proteins were predicted to follow non-classical secretion mechanisms using SecP algorithms. According to at least one of the two PSortB predictions, 48 proteins identified in the two fractions possess an unknown localization site. In addition, more than half of the proteins do not contain signal peptides recognized by current prediction programs. This suggests that known mechanisms only partly describe archaeal protein secretion. The most striking characteristic of the secretome was the high number of transport-related proteins identified from the ATP-binding cassette (ABC), tripartite ATP-independent periplasmic, ATPase, small conductance mechanosensitive ion channel (MscS), and dicarboxylate amino acid-cation symporter transporter families. In particular, identification of 21 solute-binding receptors of the ABC superfamily of the 24 predicted in silico confirms that ABC-mediated transport represents the most frequent strategy adopted by A. pernix for solute translocation across the cell membrane.

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