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Volume 109

Depolymerization dynamics of individual filaments of bacterial cytoskeletal protein FtsZ

Authors:Pablo Mateos Gil, Alfonso Paez , Ines Hörger , German Rivas , Miguel Vicente , Pedro Tarazona , Marisela Vélez Tirado
Groups of research:Biofunctional surfaces laboratory
We report observation and analysis of the depolymerization filaments
of the bacterial cytoskeletal protein FtsZ (filament temperature-
sensitive Z) formed on a mica surface. At low concentration,
proteins adsorbed on the surface polymerize forming curved filaments
that close into rings that remain stable for some time before
opening irreversibly and fully depolymerizing. The distribution of
ring lifetimes (T) as a function of length (N), shows that the rate of
ring aperture correlates with filament length. If this ring lifetime is
expressed as a bond survival time, (Tb ≡ NT), this correlation is
abolished, indicating that these rupture events occur randomly
and independently at each monomer interface. After rings open
irreversibly, depolymerization of the remaining filaments is fast,
but can be slowed down and followed using a nonhydrolyzing
GTP analogue. The histogram of depolymerization velocities of individual
filaments has an asymmetric distribution that can be fit
with a computer model that assumes two rupture rates, a slow one
similar to the one observed for ring aperture, affecting monomers
in the central part of the filaments, and a faster one affecting
monomers closer to the open ends. From the quantitative analysis,
we conclude that the depolymerization rate is affected both by nucleotide
hydrolysis rate and by its exchange along the filament,
that all monomer interfaces are equally competent for hydrolysis,
although depolymerization is faster at the open ends than in
central filament regions, and that all monomer–monomer interactions,
regardless of the nucleotide present, can adopt a curved
Keywords:bacterial division, atomic force microscopy, computer simulations, GTP hydrolysis
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