Abstract
A bacterial membrane protein ZipA that tethers FtsZ to the membrane is known to promote FtsZ assembly. In this study, the binding of ZipA to FtsZ was monitored using fluorescence spectroscopy. ZipA was found to bind to FtsZ with high affinities at three different (6.0, 6.8 and 8.0) pHs, albeit the binding affinity decreased with increasing pH. Further, thick bundles of FtsZ protofilaments were observed in the presence of ZipA under the pH conditions used in this study indicating that ZipA can promote FtsZ assembly and stabilize FtsZ polymers under unfavorable conditions. Bis-ANS, a hydrophobic probe, decreased the interaction of FtsZ and ZipA indicating that the interaction between FtsZ and ZipA is hydrophobic in nature. ZipA prevented the dilution induced disassembly of FtsZ polymers suggesting that it stabilizes FtsZ protofilaments. Fluorescein isothiocyanate-labeled ZipA was found to be uniformly distributed along the length of the FtsZ protofilaments indicating that ZipA stabilizes FtsZ protofilaments by cross-linking them.
Highlights
FtsZ is a homolog of the eukaryotic cell division protein tubulin and it plays an essential role in bacterial cell division [1,2,3,4]
Ethanesulfonic acid) (PIPES), isopropyl-b-D-thiogalactopyranoside (IPTG), guanosine 59-triphosphate sodium salt hydrate (GTP), ethylenediaminetetraacetic acid (EDTA), phenylmethylsulfonyl fluoride (PMSF), b-mercaptoethanol (b-ME), lysozyme, bovine serum albumin (BSA) and Tris-HCl were purchased from Sigma. 4,49-dianilino-1,19-binaphthyl-5,59-disulfonic acid was purchased from Molecular Probes
The cells were suspended in lysis buffer [50 mM Tris, pH 8.0, 100 mM NaCl, 1 mM ethylenediaminetetraacetic acid (EDTA), 1 mM phenylmethylsulfonyl fluoride (PMSF), 0.1% b-mercaptoethanol (b-ME) and 1 mM MgCl2] on ice
Summary
FtsZ is a homolog of the eukaryotic cell division protein tubulin and it plays an essential role in bacterial cell division [1,2,3,4]. ZipA is an early cell division protein, which is known to interact with FtsZ directly [10,11]. It enhances the FtsZ assembly and bundling in vitro [12,13]. Since the interaction between FtsZ and ZipA is essential for cell division, several inhibitors were discovered with an idea that these inhibitors may have antibacterial potential [15,16,17,18]. Impeding the FtsZ-ZipA interaction was found to block the cell division leading to long filamentous bacteria and bacterial cell death [16]. The inhibition of interaction between FtsZ and ZipA has become an important strategy for finding new class of antibacterial drugs
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