Archaic chaos: intrinsically disordered proteins in Archaea.

Bin Xue,A Keith Dunker,Christopher J Oldfield,Vladimir N Uversky,Robert W Williams

doi:10.1186/1752-0509-4-s1-s1

Abstract

BackgroundMany proteins or their regions known as intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) lack unique 3D structure in their native states under physiological conditions yet fulfill key biological functions. Earlier bioinformatics studies showed that IDPs and IDRs are highly abundant in different proteomes and carry out mostly regulatory functions related to molecular recognition and signal transduction. Archaea belong to an intriguing domain of life whose members, being microbes, are characterized by a unique mosaic-like combination of bacterial and eukaryotic properties and include inhabitants of some of the most extreme environments on the planet. With the expansion of the archaea genome data (more than fifty archaea species from five different phyla are known now), and with recent improvements in the accuracy of intrinsic disorder prediction, it is time to re-examine the abundance of IDPs and IDRs in the archaea domain.ResultsThe abundance of IDPs and IDRs in 53 archaea species is analyzed. The amino acid composition profiles of these species are generally quite different from each other. The disordered content is highly species-dependent. Thermoproteales proteomes have 14% of disordered residues, while in Halobacteria, this value increases to 34%. In proteomes of these two phyla, proteins containing long disordered regions account for 12% and 46%, whereas 4% and 26% their proteins are wholly disordered. These three measures of disorder content are linearly correlated with each other at the genome level. There is a weak correlation between the environmental factors (such as salinity, pH and temperature of the habitats) and the abundance of intrinsic disorder in Archaea, with various environmental factors possessing different disorder-promoting strengths. Harsh environmental conditions, especially those combining several hostile factors, clearly favor increased disorder content. Intrinsic disorder is highly abundant in functional Pfam domains of the archaea origin. The analysis based on the disordered content and phylogenetic tree indicated diverse evolution of intrinsic disorder among various classes and species of Archaea.ConclusionsArchaea proteins are rich in intrinsic disorder. Some of these IDPs and IDRs likely evolve to help archaea to accommodate to their hostile habitats. Other archaean IDPs and IDRs possess crucial biological functions similar to those of the bacterial and eukaryotic IDPs/IDRs.

Highlights

Introducing Archaea It is known that all the living systems on the Earth can be divided into three large domains, the Bacteria, the Archaea, and the Eucarya, each containing at least two kingdoms [1,2,3]
Archaea are similar to bacteria phenotypically, and despite a bacterial organization of archeae chromosome, these two domains of life are clearly different at the molecular level, and some of the archaea genes, metabolic pathways and proteins are more closely related to those of eukaryotes [4,5,6,7,8,9,10,11]
All eubacteria exhibit very similar subunit pattern in their RNA polymerases, whereas this pattern is not related to that seen in the archaea or the eukaryotes [4], and several archaea and eukaryotic ribosomal protein homologues have no apparent counterpart among the bacteria [5,6]

Summary

Introduction

Introducing Archaea It is known that all the living systems on the Earth can be divided into three large domains, the Bacteria, the Archaea, and the Eucarya, each containing at least two kingdoms [1,2,3]. Speaking, according to the detailed molecular analysis and comparative genomics, archaea are characterized by a combination of unique properties, such as left-handed isoprenoids containing glycerolipids, and mosaic bacterial and eukaryotic features [12]. Many proteins or their regions known as intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) lack unique 3D structure in their native states under physiological conditions yet fulfill key biological functions. With the expansion of the archaea genome data (more than fifty archaea species from five different phyla are known ), and with recent improvements in the accuracy of intrinsic disorder prediction, it is time to re-examine the abundance of IDPs and IDRs in the archaea domain

Methods

Results

Conclusion