Growing an Actin Gel on Spherical Surfaces

• Published in: Biophysical journal Vol. 78; no. 3; pp. 1643 - 1654
• Main Authors: Noireaux, V., Golsteyn, R.M., Friederich, E., Prost, J., Antony, C., Louvard, D., Sykes, C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-03-2000; Biophysical Society
• Subjects: Actins - chemistry; Actins - physiology; Actins - ultrastructure; Animals; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - physiology; Bacterial Proteins - ultrastructure; Cell-Free System; Cytosol - physiology; Gels; Glutathione Transferase - chemistry; HeLa Cells; Humans; Listeria monocytogenes - physiology; Listeria monocytogenes - ultrastructure; Membrane Proteins - chemistry; Membrane Proteins - physiology; Membrane Proteins - ultrastructure; Microscopy, Electron; Microscopy, Immunoelectron; Models, Biological; Molecular biology; Movement; Muscle, Skeletal; Proteins; Rabbits; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - ultrastructure; Surface Properties
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/S0006-3495(00)76716-6

Inspired by the motility of the bacteria
Listeria monocytogenes, we have experimentally studied the growth of an actin gel around spherical beads grafted with ActA, a protein known to be the promoter of bacteria movement. On ActA-grafted beads F-actin is formed in a spherical manner, whereas on the bacteria a “comet-like” tail of F-actin is produced. We show experimentally that the stationary thickness of the gel depends on the radius of the beads. Moreover, the actin gel is not formed if the ActA surface density is too low. To interpret our results, we propose a theoretical model to explain how the mechanical stress (due to spherical geometry) limits the growth of the actin gel. Our model also takes into account treadmilling of actin. We deduce from our work that the force exerted by the actin gel on the bacteria is of the order of 10 pN. Finally, we estimate from our theoretical model possible conditions for developing actin comet tails.