Origins of Life and Evolution of Biospheres

, Volume 41, Issue 6, pp 621–632

Molecular Evolution of Aminoacyl tRNA Synthetase Proteins in the Early History of Life

Article

DOI: 10.1007/s11084-011-9261-2

Cite this article as:
Fournier, G.P., Andam, C.P., Alm, E.J. et al. Orig Life Evol Biosph (2011) 41: 621. doi:10.1007/s11084-011-9261-2

Abstract

Aminoacyl-tRNA synthetases (aaRS) consist of several families of functionally conserved proteins essential for translation and protein synthesis. Like nearly all components of the translation machinery, most aaRS families are universally distributed across cellular life, being inherited from the time of the Last Universal Common Ancestor (LUCA). However, unlike the rest of the translation machinery, aaRS have undergone numerous ancient horizontal gene transfers, with several independent events detected between domains, and some possibly involving lineages diverging before the time of LUCA. These transfers reveal the complexity of molecular evolution at this early time, and the chimeric nature of genomes within cells that gave rise to the major domains. Additionally, given the role of these protein families in defining the amino acids used for protein synthesis, sequence reconstruction of their pre-LUCA ancestors can reveal the evolutionary processes at work in the origin of the genetic code. In particular, sequence reconstructions of the paralog ancestors of isoleucyl- and valyl- RS provide strong empirical evidence that at least for this divergence, the genetic code did not co-evolve with the aaRSs; rather, both amino acids were already part of the genetic code before their cognate aaRSs diverged from their common ancestor. The implications of this observation for the early evolution of RNA-directed protein biosynthesis are discussed.

Keywords

Aminoacyl-tRNA synthetase Paralog Genetic code LUCA Horizontal gene transfer 

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Department of Biological EngineeringMassachusetts Institute of TechnologyCambridgeUSA
  2. 2.Department of Crop and Soil SciencesCornell UniversityIthacaUSA
  3. 3.Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsUSA

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