The Chloroplast Tubulin Homologs FtsZA and FtsZB from the Red AlgaGaldieria sulphurariaCo-assemble into Dynamic Filaments.
FtsZ is a homolog of eukaryotic tubulin and is present in almost all bacteria and many archaea, where it is the major cytoskeletal protein in the Z ring, required for cell division. Unlike some other cell organelles of prokaryotic origin, chloroplasts have retained FtsZ as an essential component of the division machinery. However, chloroplast FtsZs have been challenging to study because they are difficult to express and purify. To this end, we have used a FATT tag expression system to produce as soluble proteins the two chloroplast FtsZs fromGaldieria sulphuraria, a thermophilic red alga. GsFtsZA and GsFtsZB assembled individually in the presence of GTP, forming large bundles of protofilaments. GsFtsZA also assembled in the presence of GDP, the first member of the FtsZ/tubulin superfamily to do so. Mixtures of GsFtsZA and GsFtsZB assembled protofilament bundles and hydrolyzed GTP at a rate approximately equal to the sum of their individual rates, suggesting a random co-assembly. GsFtsZA assembly by itself in limiting GTP gave polymers that remained stable for a prolonged time. However, when GsFtsZB was added, the co-polymers disassembled with enhanced kinetics, suggesting that the GsFtsZB regulates and enhances disassembly dynamics. GsFtsZA-mts (where mts is a membrane-targeting amphipathic helix) formed Z ring-like helices when expressed inEscherichia coliCo-expression of GsFtsZB (without an mts) gave co-assembly of both into similar helices. In summary, we provide biochemical evidence that GsFtsZA assembles as the primary scaffold of the chloroplast Z ring and that GsFtsZB co-assembly enhances polymer disassembly and dynamics.
From the College of Life Science, Northwest University, Xi'an, ShaanXi, China 710069.|the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and.
Yaodong
Y
Chen
the Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824-1312.
Katie
K
Porter
the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and.
Masaki
M
Osawa
the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and.
Anne Marie
AM
Augustus
the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and.
Sara L
SL
Milam
the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and.
Chandra
C
Joshi
the Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824-1312.
Katherine W
KW
Osteryoung
the Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina 27710-3709, and h.erickson@cellbio.duke.edu.
Harold P
HP
Erickson
D020418:Algal Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000737:chemistry*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000737:chemistry*; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D000461:Rhodophyta / Q000648:ultrastructure*; D040681:Structural Homology, Protein; D014404:Tubulin / Q000378:metabolism*
D020418:Algal Proteins; D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; C071525:FtsZ protein, Bacteria; D014404:Tubulin; D006160:Guanosine Triphosphate
GTPase; biophysics; cell division; cytokinesis; cytoskeleton; tubulin