Molecular and Cell Biology. Lecture 2 Replication of DNA. Pt2 Replication of prokaryotic DNA
In textbooks, replication of prokaryotic DNA, exemplified in bacteria like E. coli, initiates at a single origin of replication (oriC) where initiator proteins (DnaA) bind, recruit helicase (DnaB) to unwind the circular double-stranded DNA using the hydrolysis of ATP. This forms two replication forks. Then, the replication proceeds bidirectionally; single-strand binding proteins (SSBs) stabilize the unwound strands and primase (DnaG) synthesizes short RNA primers complementary to the template. Elongation follows with DNA polymerase III as the main replicative enzyme, synthesizing new strands continuously on the leading strand (template 3'→5') in the 5'→3' direction and discontinuously on the lagging strand as Okazaki fragments (template 5'→3'). Then, DNA polymerase I later removes RNA primers via its 5'→3' exonuclease activity, filling the gaps with dNTPs. Finally, DNA ligase seals nicks by forming phosphodiester bonds; proofreading by polymerase 3'→5' exonuclease ensures high fidelity. Termination occurs when forks meet opposite oriC, yielding two identical circular chromosomes typically in about 40 minutes.
In textbooks, replication of prokaryotic DNA, exemplified in bacteria like E. coli, initiates at a single origin of replication (oriC) where initiator proteins (DnaA) bind, recruit helicase (DnaB) to unwind the circular double-stranded DNA using the hydrolysis of ATP. This forms two replication forks. Then, the replication proceeds bidirectionally; single-strand binding proteins (SSBs) stabilize the unwound strands and primase (DnaG) synthesizes short RNA primers complementary to the template. Elongation follows with DNA polymerase III as the main replicative enzyme, synthesizing new strands continuously on the leading strand (template 3'→5') in the 5'→3' direction and discontinuously on the lagging strand as Okazaki fragments (template 5'→3'). Then, DNA polymerase I later removes RNA primers via its 5'→3' exonuclease activity, filling the gaps with dNTPs. Finally, DNA ligase seals nicks by forming phosphodiester bonds; proofreading by polymerase 3'→5' exonuclease ensures high fidelity. Termination occurs when forks meet opposite oriC, yielding two identical circular chromosomes typically in about 40 minutes.