RacA, a bacterial protein that anchors chromosomes to the cell poles.

Eukaryotic chromosomes are anchored to a spindle apparatus during mitosis, but no such structure is known during chromosome segregation in bacteria. When sister chromosomes are segregated during sporulation in Bacillus subtilis, the replication origin regions migrate to opposite poles of the cell. If and how origin regions are fastened at the poles has not been determined. Here we describe a developmental protein, RacA, that acts as a bridge between the origin region and the cell poles. We propose that RacA assembles into an adhesive patch at a centromere-like element near the origin, causing chromosomes to stick at the poles.