Differential GTP-dependentin-vitropolymerization of recombinant Physcomitrella FtsZ proteins

Abstract

AbstractCell division in bacteria and plastid division in plants both require self-assembling Filamentous temperature-sensitive Z (FtsZ) proteins as key components of their division machinery. FtsZ proteins are soluble GTPases sharing structural and biochemical similarities with eukaryotic tubulin. In the moss Physcomitrella, the morphology of the FtsZ polymer networks varies between the different FtsZ isoforms. The underlying mechanism and foundation of the distinct networks is unknown. Here, we investigated the interaction of Physcomitrella FtsZ2-1 with FtsZ1 isoformsviaco-immunoprecipitation and mass spectrometry, and found protein-protein interactionin vivo. We tagged FtsZ1-2 and FtsZ2-1 with different fluorophores and expressed both inE. coli, which led to the formation of defined structures within the cells and to an influence on bacterial cell division. Furthermore, we have optimized the purification protocols for FtsZ1-2 and FtsZ2-1 fromE. coliand characterized their GTPase activity and polymerizationin vitro. Both FtsZ isoforms showed GTPase activity, a prerequisite for polymerization. In light scattering assays, we observed GTP-dependent assembly of FtsZ1-2, but not of FtsZ2-1. In contrast, transmission electron microscopy demonstrated GTP-dependent filament formation of both isoforms. Taken together, our results reveal that Physcomitrella FtsZ1-2 and FtsZ2-1 are functionally different and that both isoforms differ in their properties from FtsZ proteins from bacteria, archaea and vascular plants.