The bacterial tubulin homolog FtsZ generates electrical oscillations

Abstract

FtsZ, a major cytoskeletal protein in all bacteria and archaea, forms a ring that directs cytokinesis. Bacterial FtsZis considered the ancestral homolog of the eukaryotic microtubule (MT)-forming tubulins, sharing GTPase activityand the ability to assemble into protofilaments, rings, and sheets, but not MTs. Previous studies from ourlaboratory demonstrated that structures of isolated brain MTs spontaneously generate electrical oscillations andbursts of electrical activity similar to action potentials. No information about whether the prokaryotic tubulinsmay share similar properties is available. Here, we obtained by ammonium sulfate precipitation an enrichedprotein fraction of the endogenous FtsZ from wild-type Escherichia coli ATCC 25922 without any transfection oroverexpression of the protein. As revealed by electron microscopy, FtsZ was detected by dot blot analysis andimmunofluorescence that assembled into filaments and sheets in a polymerization buffer. We used the patchclamptechnique to explore the electrical properties of sheets of FtsZ and bacterial cells. Electrical recordingsat various holding potentials ranging from ±200 mV showed a complex oscillatory behavior, with several peakfrequencies between 12 and 110 Hz in the power spectra and a linear mean current response. To confirm theoscillatory electrical behavior of FtsZ we also conducted experiments with commercial recombinant FtsZ, withsimilar results. We also detected, by local field potentials, similar electrical oscillations in K+-depolarized pelletsof E. coli cultures. FtsZ oscillations had a wider range of frequency peaks than MT sheets from eukaryotic origin.The findings indicate that the bacterial cytoskeleton generates electrical oscillators that may play a relevant rolein cell division and unknown signaling mechanisms in bacterial populations.