The possible role of protein-carboxyl methylation in the regulation of flagellar movement of fowl spermatozoa

Both intact and demembranated fowl spermatozoa were incubated at 30°C and 40°C with adenosine, 3-deazaadenosine and homocysteine thiolactone. This combination of products is known to block intracellular protein-carboxyl methylation reaction. The motility of intact spermatozoa incubated at 30°C was vigorous but decreased markedly after the addition of 100 μM adenosine+100 μM 3-deazaadenosine+100 μM homocysteine thiolactone. During this incubation period, the intracellular ATP concentrations of spermatozoa were maintained at approximately 40 nmol ATP/109 cells, in spite of the inhibition of motility. The motility of demembranated spermatozoa at 30°C was not inhibited by the same concentrations of blocker. At 40°C, the motility of intact spermatozoa without any effectors was almost negligible. The addition of blocker did not appreciably affect the motility of spermatozoa, which remained almost negligible. In contrast, motility became vigorous even at 40°C when intact spermatozoa were suspended in fluid to which had been added 1 mM CaCl2 or 100 nM calyculin A, a specific inhibitor of protein phosphatase-type 1 and -type 2. Stimulation of motility by Ca2+ or calyculin A was inhibited by the presence of a blocker. Contrary to that of intact spermatozoa, the motility of demembranated spermatozoa stimulated by protein phosphatase inhibitor at 40°C was not inhibited by the presence of a blocker. These results suggest that protein-carboxyl methylation may be involved in the regulation of fowl sperm motility. Furthermore, it appears that the methylating enzyme may be present in the cytoplasmic matrix and/or the plasma membrane but not retained in the axoneme and/or accessory cytoskeletal components.