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Polymers and Self Assembly: From Biology to Nanomaterials Poster Session I
18-POS
Board 18
Filament Capping Regulates the Bacterial Tubulin-Like Cytoskeleton
Bisson-Filho Alexandre
1
, Discola Karen
2
, Patricia Castellen
1,3
, Valdir Blasios
1
, Wanius Garcia
4
,
Ana Carolina Zeri
3
, Harold Erickson
5
, Andrea Dessen
2,3
,
Frederico Gueiros Filho
1
.
1
Instituto de Química - USP, São Paulo, Brazil,
2
Institut de Biologie Structurale, Grenoble,
France,
3
Brazilian Biosciences National Laboratory (LNBio), Campinas, Brazil,
4
Centro de
Ciências Naturais e Humanas, UFABC, Santo André, Brazil,
5
Duke University Medical Center,
Durham, NC, USA.
Cell division in bacteria is orchestrated by FtsZ, the tubulin ortholog of prokaryotes. At the time
of division, FtsZ self assembles into a contractile protein structure, the Z ring, and this, in turn,
remodels the bacterial envelope to achieve cytokinesis. Proteins that bind to FtsZ are key
regulators of bacterial division and valuable probes for the understanding of the fundamental
rules of FtsZ polymerization. Here we have applied biochemical and structural approaches to
determine the mechanism of FtsZ inhibition by MciZ, a 40 amino acid peptide that shuts off cell
division during spore development in Bacillus subtilis. The crystal structure of the FtsZ-MciZ
complex was solved at 3.2 Å resolution and revealed that MciZ binds to the C-terminal
polymerization interface of FtsZ, the equivalent of the minus end of tubulin. MciZ prevents the
assembly of higher order FtsZ polymers at substoichiometric levels both in vitro and in vivo.
This is not due to FtsZ monomer sequestration because FtsZ monomers self-poisoned with MciZ
are as effective as MciZ alone at inhibiting FtsZ assembly. Furthermore, EM and fluorescence
microscopy showed that MciZ binds to the ends of FtsZ filaments and shortens them. Thus,
MciZ is an FtsZ filament capping protein, the first capping protein described for the bacterial
cytoskeleton. Capping of the minus end is an unusual way of shortening filaments and indicates
that fragmentation and annealing are important reactions for FtsZ filament assembly. The effect
of MciZ on FtsZ dynamics also indicates that FtsZ filaments exhibit the same polarity as
microtubules and, thus, could undergo treadmilling.