GTP-dependent polymerization of the tubulin-like RepX replication protein encoded by the pXO1 plasmid of Bacillus anthracis.
RepX protein encoded by the pXO1 plasmid of Bacillus anthracis is required for plasmid replication. RepX harbours the tubulin signature motif and contains limited amino acid sequence homology to the bacterial cell division protein FtsZ. Although replication proteins are not known to polymerize, here we show by electron microscopy that RepX undergoes GTP-dependent polymerization into long filaments. RepX filaments assembled in the presence of GTPgammaS were more stable than those assembled in the presence of GTP, suggesting a role for GTP hydrolysis in the depolymerization of the filaments. Light scattering studies showed that RepX underwent rapid polymerization, and substitution of GTP with GTPgammaS stabilized the filaments. RepX exhibited GTPase activity and a mutation in the tubulin signature motif severely impaired its GTPase activity and its polymerization in vitro. Unlike FtsZ homologues, RepX harbours a highly basic carboxyl-terminal region and exhibits GTP-dependent, non-specific DNA binding activity. We speculate that RepX may be involved in both the replication and segregation of the pXO1 plasmid.
Anand
Syam P
SP
Department of Microbiology and Molecular Genetics, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
Akhtar
Parvez
P
Tinsley
Eowyn
E
Watkins
Simon C
SC
Khan
Saleem A
SA
D001408:Bacillus anthracis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001704:Biopolymers; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D006160:Guanosine Triphosphate / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D001704:Biopolymers; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C071525:FtsZ protein, Bacteria; D014404:Tubulin; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases