Premium
β Sliding Clamp Dynamics within E. Coli DNA Polymerase III Holoenzyme
Author(s) -
O'DONNELL MIKE
Publication year - 1994
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1994.tb52806.x
Subject(s) - citation , dna polymerase , clinical microbiology , library science , computer science , dna , biology , genetics , microbiology and biotechnology
The replicase that duplicates the E. coli chromosome, DNA polymerase I11 holoenzyme (pol I11 holoenzyme), shares in common with other cellular replicases a multiprotein structure.’ Why do chromosomal replicases consist of numerous polypeptides? There are several tasks beyond simple polymerization in the duplication of a chromosome, and these jobs require the assistance of ‘‘accessory proteins.” Some of these extra tasks, and the proteins that perform them, have been identified in several replication systems. Overall, it is remarkable how similar the different systems are. In this report, the functions of accessory proteins in the E. coli system will be examined and related to accessory protein function in other systems. Pol 111 holoenzyme of E. coli consists of 10 nonidentical subunits and has at least 18 polypeptide chains in all.*” Pol 111 holoenzyme has several special properties that distinguish it as a replicative polymerase. For example, pol 111 hydrolyzes ATP to bind tightly to a primed template and utilizes a single-stranded (ss) DNA template that is fully coated with the single-strand DNA binding protein (SSB).4,5 After pol I11 holoenzyme is locked onto DNA by ATP, it is rapid (750 nucleotideshecond) and highly processive (>lo0 kb per binding event) in synthesis without a further requirement for ATP.Upon encounter with a short heteroduplex in its path, pol I11 holoenzyme does not displace it but rather slides right over it and reinitiates processive extension without need for more The basic mechanisms by which pol I11 holoenzyme couples ATP to bind DNA, slides over duplex DNA, and achieves a high speed and processivity have been revealed through study of individual subunits of pol I11 and its subassemblies.