title: The Helicase Activity of Hyperthermophilic Archaeal MCM is Enhanced at High Temperatures by Lysine Methylation.
abstract: Lysine methylation and methyltransferases are widespread in the third domain of life, archaea. Nevertheless, the effects of methylation on archaeal proteins wait to be defined. Here, we report that recombinant sisMCM, an archaeal homolog of Mcm2-7 eukaryotic replicative helicase, is methylated by aKMT4 in vitro. Mono-methylation of these lysine residues occurs coincidently in the endogenous sisMCM protein purified from the hyperthermophilic Sulfolobus islandicus cells as indicated by mass spectra. The helicase activity of mini-chromosome maintenance (MCM) is stimulated by methylation, particularly at temperatures over 70°C. The methylated MCM shows optimal DNA unwinding activity after heat-treatment between 76 and 82°C, which correlates well with the typical growth temperatures of hyperthermophilic Sulfolobus. After methylation, the half life of MCM helicase is dramatically extended at 80°C. The methylated sites are located on the accessible protein surface, which might modulate the intra- and inter- molecular interactions through changing the hydrophobicity and surface charge. Furthermore, the methylation-mimic mutants of MCM show heat resistance helicase activity comparable to the methylated MCM. These data provide the biochemical evidence that posttranslational modifications such as methylation may enhance kinetic stability of proteins under the elevated growth temperatures of hyperthermophilic archaea.
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University Beijing, China.
authors.forename: Yisui
authors.initials: Y
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University Beijing, China.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Niu
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University Beijing, China.
authors.forename: Jiamin
authors.initials: J
authors.lastname: Cui
authors.affiliation: Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles CA, USA ; USC Norris Comprehensive Cancer Center, University of Southern California, Los Angeles CA, USA ; Department of Chemistry, University of Southern California, Los Angeles CA, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Fu
authors.affiliation: Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles CA, USA ; USC Norris Comprehensive Cancer Center, University of Southern California, Los Angeles CA, USA ; Department of Chemistry, University of Southern California, Los Angeles CA, USA.
authors.forename: Xiaojiang S
authors.initials: XS
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University Beijing, China.
authors.forename: Huiqiang
authors.initials: H
authors.lastname: Lou
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University Beijing, China.
authors.forename: Qinhong
authors.initials: Q
authors.lastname: Cao
keywords: DNA helicase; Sulfolobus; hyperthermophiles; protein methylation; thermostability