title: Characterization of a sperm factor for egg activation at fertilization of the newt Cynops pyrrhogaster.
abstract: Eggs of the newt, Cynops pyrrhogaster, arrested at the second meiotic metaphase are activated by sperm at fertilization and then complete meiosis to initiate development. We highly purified a sperm factor for egg activation from a sperm extract with several chromatographies. The purified fraction containing only a 45 kDa protein induced egg activation accompanied by an intracellular Ca2+ increase when injected into unfertilized eggs. Although injection of mouse phospholipase C (PLC) zeta-mRNA caused a Ca2+ increase and egg activation, partial amino acid sequences of the 45 kDa protein were homologous to those of Xenopus citrate synthase, but not to PLCs. An anti-porcine citrate synthase antibody recognized the 45 kDa protein both in the purified fraction and in the sperm extract. Treatment with the anti-citrate synthase antibody reduced the egg-activation activity in the sperm extract. Injection of porcine citrate synthase or mRNA of Xenopus citrate synthase induced a Ca2+ increase and caused egg activation. A large amount of the 45 kDa protein was localized in two lines elongated from the neck to the middle piece of sperm. These results indicate that the 45 kDa protein is a major component of the sperm factor for egg activation at newt fertilization.
authors.affiliation: Laboratory of Molecular Developmental Biology, Department of Applied Molecular Biosciences, Graduate School of Medicine, Yamaguchi University, 753-8512 Yamaguchi, Japan.
authors.forename: Yuichirou
authors.initials: Y
authors.lastname: Harada
authors.forename: Tamami
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Shino
authors.initials: S
authors.lastname: Hirahara
authors.forename: Akira
authors.initials: A
authors.lastname: Nakashima
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ueno
authors.forename: Shoji
authors.initials: S
authors.lastname: Oda
authors.forename: Shunichi
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Iwao
mesh_terms: D020101:Acrosome Reaction; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D005306:Fertilization; D008297:Male; D051379:Mice; D008856:Microscopy, Fluorescence; D012333:RNA, Messenger / Q000378:metabolism; D012455:Salamandridae; D013094:Spermatozoa / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D014981:Xenopus
chemical_list: D012333:RNA, Messenger; D002950:Citrate (si)-Synthase; D010738:Type C Phospholipases; D002118:Calcium