Synopsis Bacterial replicases are complex, tripartite repli-cative machines. They contain a polymerase, Pol III; a processivity factor, b 2 ; and an ATPase, DnaX complex, which loads b 2 onto DNA and chaperones Pol III onto the loaded b 2. Bacterial replicases are highly processive yet cycle rapidly during Okazaki fragment synthesis in a regulated way. Many bacteria encode both a full-length t and a shorter g form of DnaX by a variety of mechanisms. g is uniquely placed relative to two t protomers in a pentameric ring. The catalytic subunit of Pol III, a, contains a PHP domain that not only binds to prototypical e, a Mg ++-dependent exonuclease but also contains a second Zn ++-containing proofreading exonuclease, at least in some bacteria. Replication of the chromosomes of low-GC Gram-positive bacteria requires two Pol IIIs, one of which, DnaE, appears to only extend RNA primers a short distance before handing the product off to the major replicase, PolC. Other bacteria encode a second Pol III (ImuC) that apparently replaces Pol V, which is required for induced mutagenesis in E. coli.
CITATION STYLE
Julin, D. (2014). Bacteriophage and Viral Cloning Vectors. In Molecular Life Sciences (pp. 1–13). Springer New York. https://doi.org/10.1007/978-1-4614-6436-5_87-1
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