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Proc Natl Acad Sci U S A. 2011 Jan 18;108(3):1052-7. doi: 10.1073/pnas.1015397108. Epub 2010 Dec 29.

Spatial gradient of protein phosphorylation underlies replicative asymmetry in a bacterium.

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1
Department of Biology and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Abstract

Spatial asymmetry is crucial to development. One mechanism for generating asymmetry involves the localized synthesis of a key regulatory protein that diffuses away from its source, forming a spatial gradient. Although gradients are prevalent in eukaryotes, at both the tissue and intracellular levels, it is unclear whether gradients of freely diffusible proteins can form within bacterial cells given their small size and the speed of diffusion. Here, we show that the bacterium Caulobacter crescentus generates a gradient of the active, phosphorylated form of the master regulator CtrA, which directly regulates DNA replication. Using a combination of mathematical modeling, single-cell microscopy, and genetic manipulation, we demonstrate that this gradient is produced by the polarly localized phosphorylation and dephosphorylation of CtrA. Our data indicate that cells robustly establish the asymmetric fates of daughter cells before cell division causes physical compartmentalization. More generally, our results demonstrate that uniform protein abundance may belie gradients and other sophisticated spatial patterns of protein activity in bacterial cells.

PMID:
21191097
PMCID:
PMC3024676
DOI:
10.1073/pnas.1015397108
[Indexed for MEDLINE]
Free PMC Article
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