The effects of Ca2+ and ADP on dynein switching during the beat cycle of reactivated bull sperm models.

Calcium regulation of flagellar motility is the basis for chemotaxis, phototaxis, and hyperactivation responses in eukaryotic flagellates and spermatozoa. Ca2+ is the internal messenger for these responses, but the coupling between Ca2+ and the motor mechanism that generates the flagellar beat is incompletely understood. We examined the effects of Ca2+ on the flagellar curvature at the switch-points of the beat cycle in bull sperm.

The calcium response of mouse sperm flagella: role of calcium ions in the regulation of dynein activity.

Triton X-100-extracted mouse sperm treated with 0.1 mM ATP and 1.0 mM Ca(2+) exhibit an extremely coiled configuration that has been previously described as a curlicue.