Figure 1.

Localisation of Ca²⁺ store components in sperm. a; Electron microscope image of a human sperm showing the localisation of the acrosome, nucleus and mitochondria. b: immunolocalisation of InsP₃Rs (green) and nuclear pore complex proteins (red) in bovine sperm. InsP₃ receptors are localised over the acrosome (asterisks) and also at the sperm neck (arrows). Nuclear pore complex proteins indicate site of redundant nuclear envelope. c: phase image of the cells in panel b. d: immunolocalisation of secretory pathway Ca²⁺ ATPase (SPCA) (green) in human sperm. SPCA is restricted to the neck and midpiece. In many cells there is a particular concentration at the sperm neck (arrows). e: phase image of the cells in panel d. f: immunolocalisation of secretory pathway Ca²⁺ ATPase (SPCA) (green) in sperm of the sea urchin Strongylocentrotus purpuratus. SPCA localises to the giant mitochondrion in each cell (arrows). g: phase image of the cells in panel f. Panels b and c from Ho and Suarez (2003) with permission. Panels f and g from Gunaratne & Vacquier (2006) with permission.