Secreted proteins make up a significant percentage of a prokaryotic proteome and play critical roles in important cellular processes such as polymer degradation, nutrient uptake, signal transduction, cell wall biosynthesis, and motility. The majority of archaeal proteins are believed to be secreted either in an unfolded conformation via the universally conserved Sec pathway or in a folded conformation via the Twin arginine transport (Tat) pathway. Extensive in vivo and in silico analyses of N-terminal signal peptides that target proteins to these pathways have led to the development of computational tools that not only predict Sec and Tat substrates with high accuracy but also provide information about signal peptide processing and targeting. Predictions therefore include indications as to whether a substrate is a soluble secreted protein, a membrane or cell wall anchored protein, or a surface structure subunit, and whether it is targeted for post-translational modification such as glycosylation or the addition of a lipid. The use of these in silico tools, in combination with biochemical and genetic analyses of transport pathways and their substrates, has resulted in improved predictions of the subcellular localization of archaeal secreted proteins, allowing for a more accurate annotation of archaeal proteomes, and has led to the identification of potential adaptations to extreme environments, as well as phyla-specific pathways among the archaea. A more comprehensive understanding of the transport pathways used and post-translational modifications of secreted archaeal proteins will also facilitate the identification and heterologous expression of commercially valuable archaeal enzymes.
Keywords: Tat transport, Sec transport, protein transport, archaea, lipoprotein, pili, cell surface structures, archaeosortase
Citation: Szabo Z and Pohlschroder M (2012) Diversity and subcellular distribution of archaeal secreted proteins. Front. Microbio. 3:207. doi: 10.3389/fmicb.2012.00207
Received: 16 March 2012; Accepted: 21 May 2012;
Published online: 02 July 2012.
Edited by:Frank T. Robb, University of California, USA
Reviewed by:Thijs Ettema, Uppsala University, Sweden
Copyright: © 2012 Szabo and Pohlschroder. This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.
*Correspondence: Mechthild Pohlschroder, Department of Biology, University of Pennsylvania, 201 Leidy Laboratories, Philadelphia, PA 19104, USA. e-mail: firstname.lastname@example.org