In rod-shaped bacteria such as Escherichia coli and Bacillus subtilis, the FtsZ protein assembles into a ring structure, named the Z ring, which is the main component of the divisome, the cytokinetic apparatus of bacteria1. FtsZ provides a scaffold for assembly of the other divisomal proteins that positively or negatively modulate Z ring formation and participate in cell wall synthesis1. Modulator proteins are responsible for spatio-temporal regulation of septum formation, and defects in these proteins can cause defects in bacterial cell division such as filamentation and mini-cell formation2. The ZapA protein (Z ring associated protein A) is a positive modulator that assists the bundling of FtsZ polymers. ZapA promotes lateral association of FtsZ filaments and thus helps formation of a continuous Z ring from relatively short FtsZ polymers2,3. Despite its important role in cell division, the molecular details of ZapA’s interaction with FtsZ are unknown. Here we used NMR to solve the solution structure of the ZapA dimer with the goal of better understanding the molecular mechanism by which ZapA interacts with FtsZ. NMR chemical shift mapping using labelled ZapA and unlabelled FtsZ will be used to identify which ZapA residues mediate this interaction. The ZapA structure will also be useful to model the ZapA-FtsZ complex, since the FtsZ structure is already known. A model of the ZapA-FtsZ complex should help explain how ZapA assists FtsZ to form the Z ring.