%0 Journal Article
%T Extensive Lysine Methylation in Hyperthermophilic Crenarchaea: Potential Implications for Protein Stability and Recombinant Enzymes
%A Catherine H. Botting
%A Paul Talbot
%A Sonia Paytubi
%A Malcolm F. White
%J Archaea
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/106341
%X In eukarya and bacteria, lysine methylation is relatively rare and is catalysed by sequence-specific lysine methyltransferases that typically have only a single-protein target. Using RNA polymerase purified from the thermophilic crenarchaeum Sulfolobus solfataricus, we identified 21 methyllysines distributed across 9 subunits of the enzyme. The modified lysines were predominantly in -helices and showed no conserved sequence context. A limited survey of the Thermoproteus tenax proteome revealed widespread modification with 52 methyllysines in 30 different proteins. These observations suggest the presence of an unusual lysine methyltransferase with relaxed specificity in the crenarchaea. Since lysine methylation is known to enhance protein thermostability, this may be an adaptation to a thermophilic lifestyle. The implications of this modification for studies and applications of recombinant crenarchaeal enzymes are discussed. 1. Introduction Lysine methylation is found in all three domains of life. In bacteria, this posttranslational modification is restricted to a handful of ribosomal and flagellar proteins [1, 2]. In eukaryotes, lysine methylation is also restricted to a subset of proteins and catalysed by highly specific methyltransferases that can generate mono-, di-, and trimethylated lysines (reviewed in [3]). The most well-known examples are the histone proteins, where lysine methylation is carried out by sequence specific SET family methyltransferases using an S-adenosyl methionine (SAM) cofactor. These modifications result in changes in protein£¿:£¿protein interactions, chromatin structure and gene expression (reviewed in [4]). A limited number of other eukaryal proteins including notably the large subunit of Rubisco [5] are also subject to lysine methylation, though the function of these modifications is often not known [6]. More recently, proteome-wide studies of lysine methylation in the mouse brain [7] and Saccharomyces cerevisiae [8] have been added to the list of modified proteins. The latter study generated preliminary evidence for 25 monomethylated and 20 dimethylated lysines from a set of 2600 yeast proteins. The methylated proteins tended to have a higher abundance and longer half-life than average and included 11 ribosomal proteins [8]. The euryarchaeon Methanosarcina mazei encodes a clear SET-domain protein that has been shown to methylate a single lysine in the archaeal chromatin protein MC1, suggesting that mechanisms to modulate chromatin by posttranslational modification pre-date the divergence of the archaeal and eukaryal domains
%U http://www.hindawi.com/journals/archaea/2010/106341/