Advances in understanding the molecular mechanisms underlying the ultrastructural organization of bacterial cells have blurred the traditional boundaries used to distinguish eukaryotic cells from their prokaryotic counterparts. Most significant amongst these has been the demonstration that prokaryotic organisms contain functional and structural homologs of eukaryotic tubulin, actin and intermediate filaments. These cytoskeletal proteins are essential for cell division, cell shape maintenance and chromosome segregation in a variety of prokaryotic species and hold promise as targets for the discovery of new antimicrobial agents. Recently, we showed the bacterial actin homolog, MamK, is required for the subcellular organization of the magnetosome organelles of magnetotactic bacteria. These membranous organelles, used by the organism to produce nanometer-sized magnetic crystals, are organized as chains within the cell and surrounded by a distinct cytoskeletal network of filaments. In the absence of MamK this network of filaments fails to form and the magnetosomes are dispersed throughout the cell. Phylogenetic analysis shows that MamK is found outside of the magnetotactic bacteria and that it forms a distinct branch of the bacterial actin like proteins. Since it is not essential for survival and has a distinct localization within the cell it may serve as a tractable system for in-depth analysis of bacterial actin-like proteins in general. We have the following goals for this proposal. 1) Define the biochemical and biophysical properties of MamK in vitro. 2) Identify functional domains on the surface of MamK through a global mutagenesis strategy followed by a series of in vivo analyses. 3) Identify and define the function of MamK-interacting proteins. 4) Determine the genes involved in MamK assembly and magnetosome membrane formation through a genetic analysis of the magnetosome island, a large genomic region containing most of the known magnetosome genes. In addition to their relevance to bacterial actin homologs in general these findings will provide insights into the process of organelle formation in bacteria.

Public Health Relevance

Prokaryotes have been shown to contain functional and structural homologs of eukaryotic actin, tubulin and intermediate filaments. These proteins play central roles in organizing cell shape and cell division and are promising drug targets in combating pathogenic bacteria. Understanding the mechanisms that control the action of a bacterial actin homolog will provide important information for the rational design of such drugs and will elucidate key aspects of cellular organization in prokaryotes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM084122-05
Application #
8450788
Study Section
Prokaryotic Cell and Molecular Biology Study Section (PCMB)
Program Officer
Deatherage, James F
Project Start
2009-04-01
Project End
2014-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
5
Fiscal Year
2013
Total Cost
$275,842
Indirect Cost
$96,141
Name
University of California Berkeley
Department
Other Basic Sciences
Type
Schools of Earth Sciences/Natur
DUNS #
124726725
City
Berkeley
State
CA
Country
United States
Zip Code
94704
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Hershey, David M; Browne, Patrick J; Iavarone, Anthony T et al. (2016) Magnetite Biomineralization in Magnetospirillum magneticum Is Regulated by a Switch-like Behavior in the HtrA Protease MamE. J Biol Chem 291:17941-52
Hershey, David M; Ren, Xuefeng; Melnyk, Ryan A et al. (2016) MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria. PLoS Biol 14:e1002402
Rahn-Lee, Lilah; Byrne, Meghan E; Zhang, Manjing et al. (2015) A genetic strategy for probing the functional diversity of magnetosome formation. PLoS Genet 11:e1004811
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Chariaou, Michalis; Rahn-Lee, Lilah; Kind, Jessica et al. (2015) Anisotropy of bullet-shaped magnetite nanoparticles in the magnetotactic bacteria Desulfovibrio magneticus sp. Strain RS-1. Biophys J 108:1268-74
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Abreu, Nicole; Mannoubi, Soumaya; Ozyamak, Ertan et al. (2014) Interplay between two bacterial actin homologs, MamK and MamK-Like, is required for the alignment of magnetosome organelles in Magnetospirillum magneticum AMB-1. J Bacteriol 196:3111-21
Ozyamak, Ertan; Kollman, Justin; Agard, David A et al. (2013) The bacterial actin MamK: in vitro assembly behavior and filament architecture. J Biol Chem 288:4265-77
Le Sage, D; Arai, K; Glenn, D R et al. (2013) Optical magnetic imaging of living cells. Nature 496:486-9

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