Abstract
Cytokinesis in prokaryotes involves the assembly of a polymeric ring composed of FtsZ protein monomeric units. The Z ring forms at the division plane and is attached to the membrane. After assembly, it maintains a stable yet dynamic steady state. Once induced, the ring contracts and the membrane constricts. In this work, we present a computational deterministic biochemical model exhibiting this behavior. The model is based on biochemical features of FtsZ known from in vitro studies, and it quantitatively reproduces relevant in vitro data. An essential part of the model is a consideration of interfacial reactions involving the cytosol volume, where monomeric FtsZ is dispersed, and the membrane surface in the cell's mid-zone where the ring is assembled. This approach allows the same chemical model to simulate either in vitro or in vivo conditions by adjusting only two geometrical parameters. The model includes minimal reactions, components, and assumptions, yet is able to reproduce sought-after in vivo behavior, including the rapid assembly of the ring via FtsZ-polymerization, the formation of a dynamic steady state in which GTP hydrolysis leads to the exchange of monomeric subunits between cytoplasm and the ring, and finally the induced contraction of the ring. The model gives a quantitative estimate for coupling between the rate of GTP hydrolysis and of FtsZ subunit turnover between the assembled ring and the cytoplasmic pool as observed. Membrane constriction is chemically driven by the strong tendency of GTP-bound FtsZ to self-assembly. The model suggests a possible mechanism of membrane contraction without a motor protein. The portion of the free energy of GTP hydrolysis released in cyclization is indirectly used in this energetically unfavorable process. The model provides a limit to the mechanistic complexity required to mimic ring behavior, and it highlights the importance of parallel in vitro and in vivo modeling.
Highlights
One of the fundamental elements of both prokaryotic and eukaryotic cytokinesis is the assembly of a cytoskeletal ring at the future cell division plane
FtsZ is the key protein of this contractile ring. This homologue of the eukaryotic cytoskeletal protein tubulin is among the first proteins to localize at the division plane where it forms the polymeric core of the so-called Z ring
This behavior includes the assembly of the Z ring via polymerization followed by cyclization, a ‘‘dynamic steady state’’ in which rings appear stable but hydrolysis continuously leads to the exchange of monomeric subunits between cytosol and the ring, and the contraction of the ring
Summary
One of the fundamental elements of both prokaryotic and eukaryotic cytokinesis is the assembly of a cytoskeletal ring at the future cell division plane. FtsZ is the key protein of this contractile ring This homologue of the eukaryotic cytoskeletal protein tubulin is among the first proteins to localize at the division plane where it forms the polymeric core of the so-called Z ring. Homologs of FtsZ appear to be found universally in almost all bacteria and archaea, but this is not the case for other E. coli proteins utilized in ring formation. It appears that the Z ring is a universal component of prokaryotic cytokinesis but that there are species-to-species differences regarding other aspects of the process. Current knowledge of FtsZ features has been reviewed [1,2,3,4,5,6,7,8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
