This Article Full Text Full Text (PDF) Supplement All Versions of this Article: biophysj.106.082362v1 91/4/1548    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dickinson, R. B. Articles by Purich, D. L. Search for Related Content PubMed PubMed Citation Articles by Dickinson, R. B. Articles by Purich, D. L.

Diffusion Rate Limitations in Actin-Based Propulsion of Hard and Deformable Particles

Richard B. Dickinson ^*  and Daniel L. Purich 

^* Departments of Chemical Engineering, Biomedical Engineering, and Biochemistry & Molecular Biology, University of Florida Colleges of Engineering and Medicine, Gainesville, Florida

Correspondence: Address reprint requests to Dr. Richard B. Dickinson, Dept. of Chemical Engineering, University of Florida College of Engineering, PO Box 116005, Gainesville, FL 32611-6005. Tel.: 352-392-0898; E-mail: dickinso{at}che.ufl.edu.

The mechanism by which actin polymerization propels intracellular vesicles and invasive microorganisms remains an open question. Several recent quantitative studies have examined propulsion of biomimetic particles such as polystyrene microspheres, phospholipid vesicles, and oil droplets. In addition to allowing quantitative measurement of parameters such as the dependence of particle speed on its size, these systems have also revealed characteristic behaviors such a saltatory motion of hard particles and oscillatory deformation of soft particles. Such measurements and observations provide tests for proposed mechanisms of actin-based motility. In the actoclampin filament end-tracking motor model, particle-surface-bound filament end-tracking proteins are involved in load-insensitive processive insertion of actin subunits onto elongating filament plus-ends that are persistently tethered to the surface. In contrast, the tethered-ratchet model assumes working filaments are untethered and the free-ended filaments grow as thermal ratchets in a load-sensitive manner. This article presents a model for the diffusion and consumption of actin monomers during actin-based particle propulsion to predict the monomer concentration field around motile particles. The results suggest that the various behaviors of biomimetic particles, including dynamic saltatory motion of hard particles and oscillatory vesicle deformations, can be quantitatively and self-consistently explained by load-insensitive, diffusion-limited elongation of (+)-end-tethered actin filaments, consistent with predictions of the actoclampin filament-end tracking mechanism.

This article has been cited by other articles:

				V. Delatour, E. Helfer, D. Didry, K. H. D. Le, J.-F. Gaucher, M.-F. Carlier, and G. Romet-Lemonne Arp2/3 Controls the Motile Behavior of N-WASP-Functionalized GUVs and Modulates N-WASP Surface Distribution by Mediating Transient Links with Actin Filaments Biophys. J., June 15, 2008; 94(12): 4890 - 4905. [Abstract] [Full Text] [PDF]

				E. Paluch, J. v. d. Gucht, J.-F. Joanny, and C. Sykes Deformations in Actin Comets from Rocketing Beads Biophys. J., October 15, 2006; 91(8): 3113 - 3122. [Abstract] [Full Text] [PDF]