Accessory factors promote AlfA-dependent plasmid segregation by regulating filament nucleation, disassembly, and bundling.
In bacteria, some plasmids are partitioned to daughter cells by assembly of actin-like proteins (ALPs). The best understood ALP, ParM, has a core set of biochemical properties that contributes to its function, including dynamic instability, spontaneous nucleation, and bidirectional elongation. AlfA, an ALP that pushes plasmids apart in Bacillus, relies on a different set of underlying properties to segregate DNA. AlfA elongates unidirectionally and is not dynamically unstable; its assembly and disassembly are regulated by a cofactor, AlfB. Free AlfB breaks up AlfA bundles and promotes filament turnover. However, when AlfB is bound to the centromeric DNA sequence, parN, it forms a segrosome complex that nucleates and stabilizes AlfA filaments. When reconstituted in vitro, this system creates polarized, motile comet tails that associate by antiparallel filament bundling to form bipolar, DNA-segregating spindles.
Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158.
Jessica K
JK
Polka
Justin M
JM
Kollman
R Dyche
RD
Mullins
D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002503:Centromere; D004269:DNA, Bacterial / Q000378:metabolism; D009876:Operon; D010957:Plasmids; D011487:Protein Conformation
D001426:Bacterial Proteins; D004269:DNA, Bacterial
Bacillus subtilis; DNA segregation; bacterial cytoskeleton; reconstitution