Calcium regulation of an actin spring.
Calcium is essential for many biological processes involved in cellular motility. However, the pathway by which calcium influences motility, in processes such as muscle contraction and neuronal growth, is often indirect and complex. We establish a simple and direct mechanochemical link that shows how calcium quantitatively regulates the dynamics of a primitive motile system, the actin-based acrosomal bundle of horseshoe crab sperm. The extension of this bundle requires the continuous presence of external calcium. Furthermore, the extension rate increases with calcium concentration, but at a given concentration, we find that the volumetric rate of extension is constant. Our experiments and theory suggest that calcium sequentially binds to calmodulin molecules decorating the actin filaments. This binding leads to a collective wave of untwisting of the actin filaments that drives bundle extension.
Tam
Barney K
BK
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Shin
Jennifer H
JH
Pfeiffer
Emily
E
Matsudaira
P
P
Mahadevan
L
L
D000199:Actins / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000502:physiology*; D002478:Cells, Cultured; D055119:Elastic Modulus; D006737:Horseshoe Crabs; D008297:Male; D008954:Models, Biological; D008956:Models, Chemical; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000502:physiology*; D013081:Sperm Motility / Q000502:physiology*; D013094:Spermatozoa / Q000737:chemistry / Q000502:physiology*; D013314:Stress, Mechanical
D000199:Actins; D020409:Molecular Motor Proteins; D002118:Calcium
J Cell Biol. 1971 Dec;51(3):904-7
5128358
Trends Cell Biol. 2000 Aug;10(8):322-8
10884684
J Biol Chem. 1996 Feb 2;271(5):2651-7
8576236
Nature. 2004 Sep 2;431(7004):104-7
15343340
Structure. 2001 Mar 7;9(3):185-95
11286885
J Cell Biol. 2003 Sep 29;162(7):1183-8
14517201
Cell Calcium. 1995 Jun;17(6):422-30
8521456
Science. 1992 Dec 11;258(5089):1812-5
1465619
Trends Cell Biol. 2004 Jun;14(6):320-30
15183189
J Cell Biol. 1982 May;93(2):324-37
7201473
FASEB J. 1995 Jun;9(9):755-67
7601340
J Exp Biol. 1997;200(Pt 1):35-40
9317287
Biophys J. 2007 May 15;92(10):3729-33
17351007
J Cell Biol. 1975 Feb;64(2):289-310
1117029
J Mol Biol. 2004 Mar 19;337(2):255-61
15003444
Proc Natl Acad Sci U S A. 2004 Jun 29;101(26):9636-41
15210969
J Biol Chem. 1997 Aug 1;272(31):19229-35
9235915