Abstract
Helicase proteins are known to use the energy of ATP to unwind nucleic acids and to remodel protein-nucleic acid complexes. They are involved in almost every aspect of DNA and RNA metabolisms and participate in numerous repair mechanisms that maintain cellular integrity. The archaeal Lhr-type proteins are SF2 helicases that are mostly uncharacterized. They have been proposed to be DNA helicases that act in DNA recombination and repair processes in Sulfolobales and Methanothermobacter. In Thermococcales, a protein annotated as an Lhr2 protein was found in the network of proteins involved in RNA metabolism. To investigate this, we performed in-depth phylogenomic analyses to report the classification and taxonomic distribution of Lhr-type proteins in Archaea, and to better understand their relationship with bacterial Lhr. Furthermore, with the goal of envisioning the role(s) of aLhr2 in Thermococcales cells, we deciphered the enzymatic activities of aLhr2 from Thermococcus barophilus (Tbar). We showed that Tbar-aLhr2 is a DNA/RNA helicase with a significant annealing activity that is involved in processes dependent on DNA and RNA transactions.
Highlights
Introduction published maps and institutional affilHelicases are proteins that unwind nucleic acids and remodel protein-nucleic acid complexes in a wide spectrum of cellular tasks
Our initial Lhr library was composed of 1380 proteins that were identified by a similarity search against the COG1201 profile of the COG database that covers the “Lhr core” organization of Lhr helicases, i.e., the two conserved RecA1 and RecA2 domains, the winged-helix motif and the Domain 4 (Figure 1)
Because the corresponding recombinant protein was toxic when expressed in E. coli cells, we decided to perform in vitro assays with aLhr2 from T. barophilus (Tbar-aLhr2)
Summary
Helicases are proteins that unwind nucleic acids and remodel protein-nucleic acid complexes in a wide spectrum of cellular tasks. DNA helicases are critical in maintaining cellular integrity by playing important roles in DNA replication, recombination and repair. The SF1-6 share a common helicase core with a set of helicase signature motifs. SF2 members are non-hexameric helicases that share a conserved helicase core with nine characteristic motifs and that often contain N- and/or C-terminal accessory domains involved in the regulation of their activities [2,3]. The core provides the active site for ATP hydrolysis, binds nucleic acid and performs a basal unwinding activity. ATP-dependent unwinding of nucleic acid duplexes is their hallmark reaction, not iations
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