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.
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.
|Cornejo, Elias; Abreu, Nicole; Komeili, Arash (2014) Compartmentalization and organelle formation in bacteria. Curr Opin Cell Biol 26:132-8|
|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|
|Le Sage, D; Arai, K; Glenn, D R et al. (2013) Optical magnetic imaging of living cells. Nature 496:486-9|
|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|
|Komeili, Arash (2012) Molecular mechanisms of compartmentalization and biomineralization in magnetotactic bacteria. FEMS Microbiol Rev 36:232-55|
|Greene, Shannon E; Brilli, Matteo; Biondi, Emanuele G et al. (2012) Analysis of the CtrA pathway in Magnetospirillum reveals an ancestral role in motility in alphaproteobacteria. J Bacteriol 194:2973-86|
|Quinlan, Anna; Murat, Dorothee; Vali, Hojatollah et al. (2011) The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization. Mol Microbiol 80:1075-87|
|Draper, Olga; Byrne, Meghan E; Li, Zhuo et al. (2011) MamK, a bacterial actin, forms dynamic filaments in vivo that are regulated by the acidic proteins MamJ and LimJ. Mol Microbiol 82:342-54|
|Murat, Dorothee; Quinlan, Anna; Vali, Hojatollah et al. (2010) Comprehensive genetic dissection of the magnetosome gene island reveals the step-wise assembly of a prokaryotic organelle. Proc Natl Acad Sci U S A 107:5593-8|
|Topp, Shana; Reynoso, Colleen M K; Seeliger, Jessica C et al. (2010) Synthetic riboswitches that induce gene expression in diverse bacterial species. Appl Environ Microbiol 76:7881-4|