Final answer:
The β-subunit, also known as the sliding clamp, of the DNA polymerase III enzyme in prokaryotes serves the function of increasing processivity similar to PCNA in eukaryotes by forming a ring around the DNA.
Step-by-step explanation:
The subunit of the DNA polymerase III enzyme that forms a ring-like structure around DNA and acts similarly to PCNA (proliferating cell nuclear antigen) in eukaryotes to increase the enzyme's processivity in prokaryotes is the β-subunit, also known as the sliding clamp. This β-clamp forms a ring around the DNA molecule and tethers the DNA polymerase III enzyme to the DNA template, allowing for rapid and efficient synthesis of new DNA strands by preventing the polymerase from dissociating from the template.
The DNA polymerase III holoenzyme in prokaryotes, such as E. coli, is responsible for most of the DNA replication during cell division. The DNA polymerase III enzyme itself is an oligomeric assembly made up of different subunits, with the β-clamp being an essential part for its high processivity.