The assembly of MreB, a prokaryotic homolog of actin.
MreB, a major component of the bacterial cytoskeleton, exhibits high structural homology to its eukaryotic counterpart actin. Live cell microscopy studies suggest that MreB molecules organize into large filamentous spirals that support the cell membrane and play a key shape-determining function. However, the basic properties of MreB filament assembly remain unknown. Here, we studied the assembly of Thermotoga maritima MreB triggered by ATP in vitro and compared it to the well-studied assembly of actin. These studies show that MreB filament ultrastructure and polymerization depend crucially on temperature as well as the ions present on solution. At the optimal growth temperature of T. maritima, MreB assembly proceeded much faster than that of actin, without nucleation (or nucleation is highly favorable and fast) and with little or no contribution from filament end-to-end annealing. MreB exhibited rates of ATP hydrolysis and phosphate release similar to that of F-actin, however, with a critical concentration of approximately 3 nm, which is approximately 100-fold lower than that of actin. Furthermore, MreB assembled into filamentous bundles that have the ability to spontaneously form ring-like structures without auxiliary proteins. These findings suggest that despite high structural homology, MreB and actin display significantly different assembly properties.
Esue
Osigwe
O
Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
Cordero
Maria
M
Wirtz
Denis
D
Tseng
Yiider
Y
D000199:Actins / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D029968:Escherichia coli Proteins / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008027:Light; D018482:Muscle, Skeletal / Q000378:metabolism; D010710:Phosphates / Q000737:chemistry; D011485:Protein Binding; D012542:Scattering, Radiation; D013696:Temperature; D020124:Thermotoga maritima / Q000378:metabolism; D013997:Time Factors
D000199:Actins; D001426:Bacterial Proteins; D002412:Cations; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C435905:MreB1 protein, Thermotoga maritima; D010710:Phosphates; C078473:MreB protein, E coli; D000255:Adenosine Triphosphate