MUTATIONS IN FTSZ THAT CONFER RESISTANCE TO SULA AFFECT THE INTERACTION OF FTSZ WITH GTP

Mutations in the essential cell division gene ftsZ confer resistance t o SulA, a cell division inhibitor that is induced as part of the SOS r esponse. In this study we have purified and characterized the gene pro ducts of six of these mutant ftsZ alleles,ftsZ1,ftsZ2,ftsZ3,ftsZ9,ftsZ 100, and ftsZ114, and compared their properties to those of the wild-t ype gene product. The binding of GTP was differentially affected by th ese mutations. FtsZ3 exhibited no detectable GTP binding, and FtsZ9 an d FtsZ100 exhibited markedly reduced GTP binding. In contrast, FtsZ1 a nd FtsZ2 bound GTP almost as well as the wild type, and FtsZ114 displa yed increased GTP binding. Furthermore, we observed that all mutant Ft sZ proteins exhibited markedly reduced intrinsic GTPase activity. It i s likely that mutations in ftsZ that confer sulA resistance alter the conformation of the protein such that it assumes the active form.