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Proc Natl Acad Sci U S A. 2014 Feb 11;111(6):2176-81. doi: 10.1073/pnas.1304127111. Epub 2014 Jan 30.

Accessory factors promote AlfA-dependent plasmid segregation by regulating filament nucleation, disassembly, and bundling.

Author information

1
Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158.

Abstract

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.

KEYWORDS:

Bacillus subtilis; DNA segregation; bacterial cytoskeleton; reconstitution

PMID:
24481252
PMCID:
PMC3926056
DOI:
10.1073/pnas.1304127111
[Indexed for MEDLINE]
Free PMC Article
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