The helicase activity of hyperthermophilic archaeal MCM is enhanced at high temperatures by lysine methylation

Frontiers in Microbiology. 2015;6 DOI 10.3389/fmicb.2015.01247


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Journal Title: Frontiers in Microbiology

ISSN: 1664-302X (Online)

Publisher: Frontiers Media S.A.

LCC Subject Category: Science: Microbiology

Country of publisher: Switzerland

Language of fulltext: English

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Yisui eXia (China Agricultural University)

Yanling eNiu (China Agricultural University)

Jiamin eCui (China Agricultural University)

Yang eFu (University of Southern California)

Xiaojiang eChen (University of Southern California)

Huiqiang eLou (China Agricultural University)

Qinhong eCao (China Agricultural University)


Blind peer review

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Time From Submission to Publication: 14 weeks


Abstract | Full Text

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 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.