title: FtsZ Protofilament Curvature Is the Opposite of Tubulin Rings.
abstract: FtsZ protofilaments (pfs) form the bacterial cytokinetic Z ring. Previous work suggested that a conformational change from straight to curved pfs generated the constriction force. In the simplest model, the C-terminal membrane tether is on the outside of the curved pf, facing the membrane. Tubulin, a homologue of FtsZ, also forms pfs with a curved conformation. However, it is well-established that tubulin rings have the C terminus on the inside of the ring. Could FtsZ and tubulin rings have the opposite curvature? In this study, we explored the FtsZ curvature direction by fusing large protein tags to the FtsZ termini. Thin section electron microscopy showed that the C-terminal tag was on the outside, consistent with the bending pf model. This has interesting implications for the evolution of tubulin. Tubulin likely began with the curvature of FtsZ, but evolution managed to reverse direction to produce outward-curving rings, which are useful for pulling chromosomes.
authors.affiliation: Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States.
authors.forename: Max
authors.initials: M
authors.lastname: Housman
authors.affiliation: Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States.
authors.forename: Sara L
authors.initials: SL
authors.lastname: Milam
authors.affiliation: Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States.
authors.forename: Desmond A
authors.initials: DA
authors.lastname: Moore
authors.affiliation: Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States.
authors.forename: Masaki
authors.initials: M
authors.lastname: Osawa
authors.affiliation: Department of Cell Biology, Duke University, Duke University Medical Center , Durham, North Carolina 27710, United States.
authors.forename: Harold P
authors.initials: HP
authors.lastname: Erickson
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000648:ultrastructure; D010457:Peptidoglycan / Q000737:chemistry; D011487:Protein Conformation; D055503:Protein Multimerization; D014404:Tubulin / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D046912:Multiprotein Complexes; D010457:Peptidoglycan; D014404:Tubulin