FtsZ fiber bundling is triggered by a conformational change in bound GTP.
Polymer formation by the essential FtsZ protein plays a crucial role in the cytokinesis of most prokaryotes. Lateral associations between these FtsZ polymers to form bundles or sheets are widely predicted to be extremely important for FtsZ function in vivo. We have carried out a study in vitro of FtsZ polymer formation and bundling using linear dichroism (LD) to assess structural properties of the polymers. We demonstrate proof-of-principle experiments to show that LD can be used as a technique to follow FtsZ polymerization, and we present the LD spectra of FtsZ polymers. Our subsequent examination of FtsZ polymer bundling induced by calcium reveals a substantial increase in the LD signal indicative of increased polymer length and rigidity. We also detect a specific conformational change in the guanine moiety associated with bundling, whereas the conformation and configuration of the FtsZ monomers within the polymer remain largely unchanged. We demonstrate that other divalent cations can induce this conformational change in FtsZ-bound GTP coincident with polymer bundling. Therefore, we present "flipping" of the guanine moiety in FtsZ-bound GTP as a mechanism that explains the link between reduced GTPase activity, increased polymer stability, and polymer bundling.
Marrington
Rachel
R
Department of Chemistry, University of Warwick, Coventry CV4 7AL, School of Biological Sciences, Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom.
Small
Elaine
E
Rodger
Alison
A
Dafforn
Timothy R
TR
Addinall
Stephen G
SG
D001426:Bacterial Proteins / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002122:Calcium Chloride / Q000494:pharmacology; D002412:Cations; D002942:Circular Dichroism; D003598:Cytoskeletal Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry; D006147:Guanine / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D008274:Magnesium / Q000737:chemistry; D015636:Magnesium Chloride / Q000494:pharmacology; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D011108:Polymers / Q000737:chemistry; D011189:Potassium Chloride / Q000494:pharmacology; D011487:Protein Conformation; D012542:Scattering, Radiation; D013053:Spectrophotometry; D013997:Time Factors; D014466:Ultraviolet Rays
D001426:Bacterial Proteins; D002412:Cations; D003598:Cytoskeletal Proteins; C071525:FtsZ protein, Bacteria; D011108:Polymers; D015636:Magnesium Chloride; D006147:Guanine; D011189:Potassium Chloride; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D008274:Magnesium; D002122:Calcium Chloride; D002118:Calcium