Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 64

Additional complications of DNA replication come from the fact that the DNA is double stranded and the strands are antiparallel. The replication of all bacterial chromosomes begins at one point, called the origin of replication, with the replication enzymes moving in opposite directions from this point along the chromosome. In this process, both strands of DNA are replicated at the same time with a coordinated set of proteins. Replicating the antiparallel strands is further complicated by the abovementioned fact that DNA polymerases can replicate only in the 5′-to-3′ direction. Therefore, one DNA strand is replicated in the same direction that the replication fork is moving, and in theory, replication of this strand could continue without the need for reinitiating in a process called leading-strand DNA synthesis. However, replication of the other DNA strand occurs in the opposite direction from the progression of the replication machinery. Replication of this strand must continually be reinitiated in a process known as lagging-strand DNA synthesis. Replication of double-stranded DNA requires coordination between multiple holoenzyme subunits and DNA polymerases, as well as a host of other replication proteins.