and chemistry of many replisome factors (such as the AAA+ ATPase features of the individual clamp loading sub-units, along with the helical conformation they adopt), and the associations between clamp loading factors and other accessory factors, also increases processivity. To this point, according to research by Kuriyan et al., due to their role in recruiting and binding other factors such as priming enzymes and replicative polymerases, clamp loaders and sliding clamps are at the heart of the replisome machinery. Research has found that clamp loading and sliding clamp factors are absolutely essential to replication, which explains the high degree of structural conservation observed for clamp loading and sliding clamp factors. This architectural and structural conservation is seen in organisms as diverse as bacteria, phages, yeast, and humans. That such a significant degree of structural conservation is observed without sequence homology further underpins the significance of these structural solutions to replication challenges. Clamp loader Clamp loader is a generic term that refers to replication factors called gamma (bacteria) or RFC (eukaryotes). The combination of template DNA and primer RNA is referred to as 'A-form DNA' and it is thought that clamp loading replication proteins (helical heteropentamers) want to associate with A-form DNA because of its shape (the structure of the major/minor groove) and chemistry (patterns of hydrogen bond donors and acceptors). Thus, clamp loading proteins associate with the primed region of the strand which causes hydrolysis of ATP and provides energy to open the clamp and attach it to the strand. Sliding clamp Sliding clamp is a generic term that refers to ring-shaped replication factors called beta (bacteria) or PCNA (eukaryotes and archaea). Clamp proteins attract and tether replicative polymerases, such as DNA polymerase III, in order to extend the amount of time that a replicative polymerase stays associated with the strand. From a chemical perspective, the clamp has a slightly positive charge at its centre that is a near perfect match for the slightly negative charge of the DNA strand. In some organisms, the clamp is a dimer, and in other organisms the clamp is a trimer. Regardless, the conserved ring architecture allows the clamp to enclose the strand. Dimerisation of replicative polymerases Replicative polymerases form an asymmetric dimer at the replication fork by binding to sub-units of the clamp loading factor. This asymmetric conformation is capable of simultaneously replicating the leading and lagging strands, and the collection of factors