Chapter title |
The Eukaryotic Mcm2-7 Replicative Helicase
|
---|---|
Chapter number | 7 |
Book title |
The Eukaryotic Replisome: a Guide to Protein Structure and Function
|
Published in |
Sub cellular biochemistry, January 2012
|
DOI | 10.1007/978-94-007-4572-8_7 |
Pubmed ID | |
Book ISBNs |
978-9-40-074571-1, 978-9-40-074572-8
|
Authors |
Sriram Vijayraghavan, Anthony Schwacha |
Abstract |
In eukaryotes, the Mcm2-7 complex forms the core of the replicative helicase - the molecular motor that uses ATP binding and hydrolysis to fuel the unwinding of double-stranded DNA at the replication fork. Although it is a toroidal hexameric helicase superficially resembling better-studied homohexameric helicases from prokaryotes and viruses, Mcm2-7 is the only known helicase formed from six unique and essential subunits. Recent biochemical and structural analyses of both Mcm2-7 and a higher-order complex containing additional activator proteins (the CMG complex) shed light on the reason behind this unique subunit assembly: whereas only a limited number of specific ATPase active sites are needed for DNA unwinding, one particular ATPase active site has evolved to form a reversible discontinuity (gate) in the toroidal complex. The activation of Mcm2-7 helicase during S-phase requires physical association of the accessory proteins Cdc45 and GINS; structural data suggest that these accessory factors activate DNA unwinding through closure of the Mcm2-7 gate. Moreover, studies capitalizing on advances in the biochemical reconstitution of eukaryotic DNA replication demonstrate that Mcm2-7 loads onto origins during initiation as a double hexamer, yet does not act as a double-stranded DNA pump during elongation. |
Mendeley readers
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Demographic breakdown
Readers by professional status | Count | As % |
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Student > Master | 3 | 10% |
Other | 0 | 0% |
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Unknown | 7 | 24% |