The International Journal of Biochemistry & Cell Biology 50 (2014) 38–46 Contents lists available at ScienceDirect The International Journal of Biochemistry & Cell Biology jo u r n al homep ag e: www.elsevier.com/locate/biocel FtsZ Dr , a tubulin homologue in radioresistant bacterium Deinococcus radiodurans is characterized as a GTPase exhibiting polymerization/depolymerization dynamics in vitro and FtsZ ring formation in vivo Kruti Mehta Modi a , Raghvendra Tewari b , Hari Sharan Misra a,∗ a Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai 400085, India b Material Science Division, Bhabha Atomic Research Centre, Mumbai 400085, India a r t i c l e i n f o Article history: Received 15 October 2013 Received in revised form 10 January 2014 Accepted 20 January 2014 Available online 3 February 2014 Keywords: Bacterial cell division Deinococcus FtsZ-GTPase Protein polymerization Radioresistance a b s t r a c t The GTPase-dependent polymerization/depolymerization dynamics of FtsZ regulate bacterial cell division in vivo. Deinococcus radiodurans is better known for its extraordinary radioresistance and therefore, the characterization of FtsZ of this bacterium (FtsZ Dr ) would be required to understand the mechanisms underlying regulation of cell division in response to DNA damage. Recombinant FtsZ Dr bound to GTP and showed GTPase activity. It produced bundles of protofilaments in the presence of either GTP or Mg 2+ ions. But the formation of the higher size ordered structures required both GTP and Mg 2+ in vitro. It showed polymerization/depolymerization dynamics as a function of GTP and Mg 2+ . Interestingly, ATP interacted with FtsZ Dr and stimulated its GTPase activity by ∼2-fold possibly by increasing both substrate affinity and rate of reaction. FtsZ Dr -GFP expressing in D. radiodurans produced typical Z ring perpendicular to the plane of first cell division. These results suggested that FtsZ Dr is a GTPase in vitro and produces typical Z ring at the mid cell position in D. radiodurans. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Cell division in bacteria is a highly ordered process involving a large number of proteins forming a higher order complex called the divisome (Margolin, 2005). FtsZ is one of the highly conserved proteins of this complex. FtsZ orthologs have been identified in bacteria, archea, chloroplasts and the mitochondria of some algae and amoebae (Gilson and Beech, 2001). FtsZ like tubulin is a GTPase and undergoes GTP dependent polymerization in head-to-tail fash- ion (de Boer et al., 1992; Bramhill and Thompson, 1999; Oliva et al., 2004). The GTPase activity of FtsZ and its effect on poly- merization and depolymerization dynamics is regulated differently in different bacteria (Adams and Errington, 2009). In vitro FtsZ- GTP produces different lengths of polymer, which after attaining a critical length undergo GTP hydrolysis and results in depoly- merization, and thereby the release of monomer in the form of FtsZ-GDP (Scheffers et al., 2002). The protofilaments may exist as ∗ Corresponding author. Tel.: +91 22 25595417; fax: +91 22 25505151. E-mail addresses: hsmisra@barc.gov.in, harimisra38@yahoo.com, harimisra38@rediffmail.com (H.S. Misra). single filaments or laterally associate to form bundles and sheets in the presence of added cofactors and/or proteins (Yu and Margolin, 1997; Mukherjee and Lutkenhaus, 1999; Hale et al., 2000; Erickson et al., 2010). In certain cases, lateral interactions can affect the GTPase activity and stability of the protofilaments. In vivo, FtsZ polymerizes into ring like structure termed the Z-ring at the cell division site, which undergoes depolymerization in a tightly reg- ulated manner and brings about cytokinesis. Negative regulatory systems like ‘Min’ and ‘NOC’ (nucleoid occlusion) bring about both spatial and temporal regulation of Z ring formation in vivo (Barak and Wilkinson, 2007). The FtsZ ring dynamics is intrinsic to the structure of this protein and its stability is influenced by surround- ing microenvironment. Therefore, the regulation of polymerization and depolymerization dynamics of FtsZ should presumably be dif- ferent in different bacteria and influence the rates of cell division under different growth conditions. Deinococcus radiodurans, an extraordinarily radioresistant bac- terium grows as diplococci and tetracocci with a doubling time of ∼90 min under normal growth conditions (Slade and Radman, 2011). It survives the lethal and mutagenic effects of several DNA- damaging agents including radiation and desiccation without a measurable loss of cell viability (Battista, 2000). D. radiodurans 1357-2725/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biocel.2014.01.015