E. coli replisome structure

Replisome is a multiple protein complex that works together on the template in order to synthesize new DNA. Basically,  E. coli replisome contains a hexamer helicase, single stranded binding protein SSB, primase DnaG, 2 Polymerase III core, a gamma complex (also known as clamp loader) and β clamp. Helicase is a homohexamer that encircles the lagging strand like a ring. It translocates along the ssDNA and separate the duplex DNA using energy from ATP hydrolysis. The unwinding of double stranded DNA and discontinuous synthesis of lagging strand leaves Continue Reading →

Overview of 5 DNA polymerases in E. coli cell

So far, there are 5 distinct DNA polymerases have been found in E. coli cell: Pol I, Pol II, Pol III, Pol IV, and Pol V. While Pol III (Pol III Holoenzyme) is a primary polymerase involved in DNA replication, the others take part in other processes such as DNA repair, translesion synthesis … rather than in chromosome replication. Pol I is encoded by polA gene and belongs to the A family. During DNA replication, PoI synthesizes the gap between Okazaki fragments to complete lagging product synthesis by its 5′-3′ polymerase activity. Continue Reading →