EF-hand motif found in phosphoinositide phospholipase C zeta 1 (PI-PLC-zeta1)
PI-PLC-zeta1, also termed 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase zeta-1, or phospholipase C-zeta-1 (PLC-zeta-1), or testis-development protein NYD-SP27, is only found in the testis. The sperm-specific PI-PLC plays a fundamental role in vertebrate fertilization by initiating intracellular calcium oscillations that trigger the embryo development. However, the mechanism of its activation still remains unclear. PI-PLC-zeta1 contains an N-terminal four atypical EF-hand motifs, a PLC catalytic core domain, and a C-terminal C2 domain. The PLC catalytic core domain is a TIM barrel with two highly conserved regions (X and Y) split by a highly degenerate linker sequence. Unlike other PI-PLCs, PI-PLC-zeta is responsible for Ca2+ oscillations in fertilized oocytes and exhibits a high sensitivity to Ca2+ mediated through its EF-hand domain. There is only one PLC-zeta isozyme. Aside from PI-PLC-zeta identified in mammals, its eukaryotic homologs have been classified with this family.