Abstract
Archaea encode a eukaryotic-type primase comprising a catalytic subunit (PriS) and a noncatalytic subunit (PriL). Here we report the identification of a primase noncatalytic subunit, denoted PriX, from the hyperthermophilic archaeon Sulfolobus solfataricus. Like PriL, PriX is essential for the survival of the organism. The crystallographic analysis complemented by sensitive sequence comparisons shows that PriX is a diverged homologue of the C-terminal domain of PriL but lacks the iron-sulfur cluster. Phylogenomic analysis provides clues on the origin and evolution of PriX. PriX, PriL and PriS form a stable heterotrimer (PriSLX). Both PriSX and PriSLX show far greater affinity for nucleotide substrates and are substantially more active in primer synthesis than the PriSL heterodimer. In addition, PriL, but not PriX, facilitates primer extension by PriS. We propose that the catalytic activity of PriS is modulated through concerted interactions with the two noncatalytic subunits in primer synthesis.
Highlights
Archaea encode a eukaryotic-type primase comprising a catalytic subunit (PriS) and a noncatalytic subunit (PriL)
Given that PriSL from S. solfataricus is known to possess unusual properties unexpected for the proposed role of the enzyme in DNA replication, we set out to determine if there existed additional proteins that might modulate the activity of PriSL
By using a co-immunoprecipitation assay, we found that an unknown protein was consistently immunoprecipitated with antibodies against PriS or PriL (Fig. 1a)
Summary
Archaea encode a eukaryotic-type primase comprising a catalytic subunit (PriS) and a noncatalytic subunit (PriL). The eukaryotic primases are a heterodimer of a small catalytic subunit (PriS or p48) and a large noncatalytic subunit (PriL or p58), which form a complex with DNA polymerase a (Pol a or p180) and the B subunit (p70)[3]. Surprising is the observation that PriSL from S. solfataricus was nearly inactive in primer synthesis in vitro at high temperatures that are optimal for the growth of this organism[15] It remains unclear how the eukaryotic-type primase serves its proposed physiological role in Archaea. We report the identification of a primase noncatalytic subunit, denoted PriX, from S. solfataricus and show that PriX, PriS and PriL form a unique heterotrimeric primase complex capable of far more efficient primer synthesis than PriSL
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
