This axonemal protein participates in an energy shuttle that utilizes phosphocreatine to transfer the energy from ATP generated by the mitochondrion in the sperm head to dynein in the distal portions of the flagellum. ATP + creatine = ADP + H(+) + N-phosphocreatine Monomer. Associates specifically with the axoneme and may bind directly to polymerized microtubules. Contains three complete but non-identical creatine kinase segments flanked by unique regions. Belongs to the ATP:guanido phosphotransferase family.