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Archaea, 2
© 2005 Heron Publishing—Victoria, Canada
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The archaeal origins of the eukaryotic translational system

Hyman Hartman (1, 2), Paola Favaretto (2) and Temple F. Smith (2, 3)

1. Biological Engineering Division, Building 56, Room 354, Massachusetts Institute of Technology, Cambridge MA 02139, USA / 2. BioMolecular Engineering Research Center, Boston University, 36 Cummington St., Boston MA 02215, USA / 3. Corresponding Author ([email protected]) / Received June 7, 2005; accepted October 5, 2005; published online November 9, 2005


Among the 78 eukaryotic ribosomal proteins, eleven are specific to Eukarya, 33 are common only to Archaea and Eukarya and 34 are homologous (at least in part) to those of both Bacteria and Archaea. Several other translational proteins are common only to Eukarya and Archaea (e.g., IF2a, SRP19, etc.), whereas others are shared by the three phyla (e.g., EFTu/EF1A and SRP54). 

Although this and other analyses strongly support an archaeal origin for a substantial fraction of the eukaryotic translational machinery, especially the ribosomal proteins, there have been numerous unique and ubiquitous additions to the eukaryotic translational system besides the 11 unique eukaryotic ribosomal proteins. These include peptide additions to most of the 67 archaeal homolog proteins, rRNA insertions, the 5.8S RNA and the Alu extension to the SRP RNA. Our comparative analysis of these and other eukaryotic features among the three different cellular phylodomains supports the idea that an archaeal translational system was most likely incorporated by means of endosymbiosis into a host cell that was neither bacterial nor archaeal in any modern sense. Phylogenetic analyses provide support for the timing of this acquisition coinciding with an ancient bottleneck in prokaryotic diversity.

Keywords: Crenarchaea, eukaryotic origin, evolution, ribosome.

 ISSN 1472-3654 (Online) ISSN 1472-3646 (Print) Copyright © 2002–2007 Heron Publishing