Role of arginine kinase in Paramecium tetraurelia (Ciliophora, Peniculida): Subcellular localization of AK3 and phosphoarginine shuttle system in cilia.

The ciliate Paramecium tetraurelia has four arginine kinase genes (AK1, AK2, AK3, and AK4). Of these genes, only AK3 has a signal sequence for farnesylation, a post-translational modification that enables anchoring of the modified enzyme to the ciliary membrane. To confirm this modification, AK3 was synthesized using a cell-free protein synthesis system and the peptide masses were analyzed using peptide mass fingerprinting (PMF).