Main steps of DNA replication in bacteria. a) Initiation of DNA replication; the datA locus has a high affinity for binding DnaA (1). DnaA binds to ATP, homo-multimers of DnaA-ATP are formed (2). These homo-multimers bind to oriC and once replication is initiated SeqA binds this region and prevents initiation of a new replication event (3). The SSB (single strand binding) protein and DnaB assist the complex to open the DNA strands and release DnaC (4). A DNA topoisomerase helps to further unfold the DNA strands (5). b) The elongation phase; the replication fork is formed and the replisome is assembled (6). DNA polymerase III replicates the leading strand (7). DnaG incorporates RNA primers as primers for replication of the lagging strand (8). Polymerase III can now replicate Okazaki fragments on the lagging strand (9). DNA polymerase I replaces RNA nucleotides for DNA nucleotides (10). A DNA ligase (LigA) seals the nicks on contiguous DNA fragments (11). c) Termination of DNA replication; The protein Tus binds to the ter sites, when replisomes reach Tus, replication ceases (12). The recombinases XerC and XerD resolve the replicated DNA strands (13). Finally, FtsK translocates the DNA strands and each double-stranded DNA molecule can be liberated (14).

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Context 1

... whole process concludes when replisomes reach the ter site, almost opposite to oriC on the circular DNA molecule. Tus proteins are attached to the ter sites and when replisomes reach these complexes, they collide and finally are disassembled (see Figure 1 for an overview of the whole process). ...