IDENTIFICATION OF 2 DISTINCTLY LOCALIZED MITOCHONDRIAL CREATINE-KINASE ISOENZYMES IN SPERMATOZOA

The creatine kinase (CK) isoenzyme system is essential for motility in rooster and sea urchin sperm, In the present study, biochemical chara cterization as well as immunofluorescence and confocal laser microscop y with highly specific antibodies against various chicken CK isoenzyme s revealed that cytosolic brain-type CK isoenzyme(B-CK) is the only CK isoenzyme in rooster seminal plasma, while three isoenzymes, cytosoli c B-CK, sarcomeric mitochondrial CK (Mi(b)-CK), and a variant of ubiqu itous Mi-CK ('Mi(a)-CK variant'), are found in rooster spermatozoa, Th ese three isoenzymes are localized in different regions of the sperm c ell, B-CK and Mi(b)-CK were localized along the entire sperm tail and in the mitochondria-rich midpiece, respectively, The 'Mi(a)-CK variant ', on the other hand, was found predominantly at the head-midpiece bou ndary, in a non-uniform manner in the midpiece itself and, surprisingl y, at the distal end of the sperm tail as well as at the acrosome, Sev eral lines of evidence show that the 'Mi(a)-CK variant' shares some ch aracteristics with purified Mi(a)-CK from chicken brain, but also disp lays distinctive features, This is the first evidence for two differen t Mi-CK isoenzymes occurring in one cell and, additionally, for the co expression of Mi(b)-CK and cytosolic brain-type B-CK in the same cell, The relevance of these findings for sperm physiology and energetics i s discussed.