xerD

XerD is a bacterial site-specific recombinase that participates in chromosome dimer resolution, typically functioning together with XerC as part of the XerC/XerD recombination system. It belongs to the family of tyrosine recombinases that act on specific DNA sequences to rearrange DNA topology during replication.

In most bacteria, a circular chromosome can form dimeric molecules during replication. The XerC/XerD recombinases act at the chromosomal dif site to convert dimers into monomers, restoring proper chromosome segregation. XerD generally plays the initiating role in the strand exchange at dif, with XerC completing the reaction; the process is activated by the cell division protein FtsK, which helps align the XerC/XerD complex and stimulate catalysis. The coordinated action of XerD and XerC ensures accurate termination of replication and separation of daughter chromosomes.

Genetically, xerD is typically encoded by a gene named xerD and is often located in close proximity to xerC in the bacterial genome, forming a conserved operon or gene cluster in many Gram-negative bacteria. The XerC/XerD system is widely conserved, though some bacterial lineages exhibit variations in regulatory controls or in the reliance on auxiliary proteins for efficient dimer resolution.

XerD’s function is essential for maintaining genome stability and proper cell division in many species, though the indispensability can vary by organism and context. It is studied primarily in the context of bacterial chromosome maintenance and the mechanisms that ensure faithful chromosome segregation during cell division. See also XerC, dif site, and FtsK.