Bending stiffness of a crystalline actin bundle.
The acrosomal process of the sperm of the horseshoe crab (Limulus polyphemus) is a unique crystalline actin bundle, consisting of multiple actin filaments cross-linked by the actin-bundling protein, scruin. For successful fertilization, the acrosomal bundle must penetrate through a 30 microm thick jelly coat surrounding the egg and thus it must be sufficiently stiff. Here, we present two measurements of the bending stiffness of a single crystalline bundle of actin. Results from these measurements indicate that the actin:scruin composite bundle has an average elastic modulus of 2 GPa, which is similar to that of a single actin filament, and a bending stiffness that is more than two orders of magnitude larger than that of a bundle of uncross-linked actin filaments due to stiffening by the scruin matrix.
Department of Mechanical Engineering, M.I.T., Cambridge, MA 02139, USA.
Jennifer H
JH
Shin
L
L
Mahadevan
P T
PT
So
Paul
P
Matsudaira
D000177:Acrosome / Q000737:chemistry* / Q000502:physiology; D000199:Actins / Q000737:chemistry* / Q000502:physiology; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D003460:Crystallization; D004548:Elasticity; D005260:Female; D006737:Horseshoe Crabs; D066298:In Vitro Techniques; D008280:Magnetics; D008297:Male; D013084:Sperm-Ovum Interactions / Q000502:physiology
D000199:Actins; C083765:scruin protein, Horseshoe Crab