Calcium sensors in sea urchin sperm flagella
Version of Record online: 4 FEB 2005
Copyright © 1991 Wiley-Liss, Inc.
Cell Motility and the Cytoskeleton
Volume 18, Issue 2, pages 123–130, 1991
How to Cite
Brokaw, C. J. (1991), Calcium sensors in sea urchin sperm flagella. Cell Motil. Cytoskeleton, 18: 123–130. doi: 10.1002/cm.970180207
- Issue online: 4 FEB 2005
- Version of Record online: 4 FEB 2005
- Manuscript Accepted: 25 OCT 1990
- Manuscript Received: 20 JUL 1990
The asymmetry of ATP-reactivated flagellar bending waves of Triton-demem-brated sea urchin spermatozoa has been measured over a range of free Ca2+ ion concentrations from 10−9 to 10−4 M. Detailed examination of the gradual response of asymmetry to Ca2+ ion concentration over this wide range indicates the presence of two Ca2+ sensors. A high-affinity sensor operates at Ca2+ concentrations near 10−7.5 M. A lower-affinity sensor operates at Ca2+ concentrations above 10−6 M, in the typical range for calmodulin-mediated responses. Incubation of demembranated sperm flagella at high Ca2+ concentrations to release calmodulin is required to enable these Ca2+ responses to be observed. This treatment also causes a decrease in the apparent affinity of the flagella for cal-modulin, as determined by measuring the increase in asymmetry in response to addition of exogenous calmodulin at low Ca2+ concentration.