ATP (adenosine triphosphate) provides the energy necessary for several key steps in DNA replication. One critical use of ATP is by DNA ligase to seal broken phosphodiester bonds.
The Role of ATP in DNA Ligation
DNA ligase is an enzyme that repairs single-stranded breaks, or "nicks," in the DNA backbone during replication and repair processes. These nicks occur when there is a missing phosphodiester bond between adjacent nucleotides. The DNA ligase reaction, which requires ATP, proceeds in two key steps as described in Figure 5-14:
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Activation of the 5' end: DNA ligase utilizes ATP to activate the 5' end of the DNA strand at the nick. This activation involves transferring an AMP (adenosine monophosphate) moiety from ATP to the 5' phosphate group.
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Formation of the new bond: The activated 5' end then facilitates the formation of a phosphodiester bond with the adjacent 3' hydroxyl group, effectively sealing the nick and restoring the integrity of the DNA strand.
In essence, ATP provides the necessary energy for DNA ligase to catalyze the formation of a phosphodiester bond, a crucial step in completing and repairing DNA strands during replication.
