title: Sperm proteases and extracellular ubiquitin-proteasome system involved in fertilization of ascidians and sea urchins.
abstract: Ascidians (primitive chordates) are hermaphroditic animals that release spermatozoa and eggs almost simultaneously, but some species, including Halocynthia roretzi, show strict self-sterility. In H. roretzi, a 70-kDa vitelline coat (VC) protein consisting of 12 EGF-like repeats, named HrVC70, appears to be a promising candidate for the self/nonself-recognition (or allorecognition) system during gamete interaction. After spermatozoon recognizes the VC as nonself, sperm 700-kDa extracellular ubiquitin-conjugating enzyme complex appears to ubiquitinate Lys234 of HrVC70, and the ubiquitinated HrVC70 is degraded by the sperm 26S proteasome that is located on the sperm head surface. This novel ubiquitin-proteasome system enables spermatozoa to penetrate through the VC. Sperm trypsin-like proteases, acrosin and spermosin, also participate in fertilization, probably as sperm-side 'movable' binding proteins to the VC.
authors.affiliation: Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, 429-63 Sugashima, Toba, 517-0004, Mie Prefecture, Japan, hsawada@bio.nagoya-u.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sawada
authors.forename: Masako
authors.initials: M
authors.lastname: Mino
authors.forename: Mari
authors.initials: M
authors.lastname: Akasaka
mesh_terms: D000818:Animals; D004527:Egg Proteins / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D005306:Fertilization; D008297:Male; D010447:Peptide Hydrolases / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000502:physiology*; D012617:Sea Urchins / Q000502:physiology*; D013094:Spermatozoa / Q000201:enzymology*; D025801:Ubiquitin / Q000502:physiology*; D014561:Urochordata / Q000502:physiology*
chemical_list: D004527:Egg Proteins; D025801:Ubiquitin; C035651:vitelline membrane proteins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex