title: Bovine seminal plasma aSFP: localization of disulfide bridges and detection of three different isoelectric forms.
abstract: Acidic seminal fluid protein (aSFP) is a major 13 kDa protein isolated from bull seminal plasma and characterized as a new growth factor which stimulates in vitro cell division and progesterone secretion by ovarian cells. Here, we establish that the four cysteines of oxidized aSFP form two disulfide bridges between nearest-neighbour residues. This pattern is conserved in boar spermadhesins, with which aSFP shares up to 50% amino acid sequence identity, and other proteins of the recently identified CUB domain family. Using isoelectric focusing in combination with sulfhydryl group-specific blotting, the three forms of aSFP were identified as completely oxidized (pI 4.7), partly reduced (pI 4.8) and fully reduced at pI 5.1. These results indicate that native aSFP possesses two pairs of cysteine residues of different reactivity. The observation that aSFP can protect sperm from oxidative damage might be explained by its reduction/oxidation behaviour.
authors.affiliation: Institut für Physiologie, Forschungszentrum für Milch und Lebensmittel-Weihenstephan, Freising, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Einspanier
authors.forename: I
authors.initials: I
authors.lastname: Krause
authors.forename: J J
authors.initials: JJ
authors.lastname: Calvete
authors.forename: E
authors.initials: E
authors.lastname: Töfper-Petersen
authors.forename: H
authors.initials: H
authors.lastname: Klostermeyer
authors.forename: H
authors.initials: H
authors.lastname: Karg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry*; D004229:Dithiothreitol / Q000494:pharmacology; D007525:Isoelectric Focusing; D007526:Isoelectric Point; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D029584:Prostatic Secretory Proteins; D011506:Proteins / Q000737:chemistry*; D012661:Semen / Q000737:chemistry*; D029589:Seminal Plasma Proteins; D014357:Trypsin / Q000378:metabolism
chemical_list: D004220:Disulfides; D010446:Peptide Fragments; D029584:Prostatic Secretory Proteins; D011506:Proteins; D029589:Seminal Plasma Proteins; C043076:beta-microseminoprotein; D014357:Trypsin; D003545:Cysteine; D004229:Dithiothreitol