Plasmid copies are paired around a centromere-like site and then separated in the two daughter cells. Partition systems involve three elements, organized in an auto-regulated operon:
* A centromere-like DNA site
* Centromere binding proteins (CBP)
* The motor protein
The centromere-like DNA site is required in cis for plasmid stability. It often contains one or more inverted repeats which are recognized by multiple CBPs. This forms a nucleoprotein complex termed the partition complex. This complex recruits the motor protein, which is a nucleotide triphosphatase (NTPase). The NTPase uses energy from NTP binding and hydrolysis to directly or indirectly move and attach plasmids to specific host location (e.g. opposite bacterial cell poles).
The partition systems are divided in four types, based primarily on the type of NTPases:
* Type I : Walker type P-loop ATPase
* Type II : Actin-like ATPase
* Type III : tubulin-like GTPase
* Type IV : No NTPase