**Phosphorylation/dephosphorylation of threonine residues:**

Among the proteins that were phosphorylated following motility activation in fresh sperm (Fig. 7B), two bands (named 15-9ThP and 147ThP) were phosphorylated after activation in frozen–thawed spermatozoa (Fig. 9B). However, it must be underlined that within the proteins belonging to the 15-9 ThP band, only one (11 kDa) previously identified as acetylcoenzyme A synthetase (Zilli et al, 2008a) was phosphorylated after motility activation in cryopreserved sperm (Fig. 9B).
