Prokaryotic DNA Replication : DNA ligase and Termination
 

DNA ligase
The final phosphodiester linkage between the 5′-phosphate group on the DNA synthesized by DNA pol III and the 3′-hydroxyl group on the DNA made by DNA pol I is catalyzed by DNA ligase (Fig. 1). The joining of these two stretches of DNA requires energy, which in most organisms is provided by the cleavage of ATP to adenosine monophosphate + PPi.

Figure 1: Formation of a phosphodiester bond by DNA ligase. [Note: Adenosine monophosphate (AMP) is first linked to ligase, then to the 5′-phosphate, and then released.]
 Termination
Replication termination in E. coli is mediated by sequence-specific binding of the protein Tus (terminus utilization substance) to replication termination (ter) sites on the DNA, stopping the movement of the replication fork.