A fragment of prosaposin (SGP-1) from rooster sperm promotes sperm-egg binding and improves fertility in chickens.
A protein isolated from the supernatant of cryopreserved rooster sperm was found to increase the capability of cryopreserved rooster sperm to bind in vitro to the perivitelline membrane of a chicken egg and substantially raise fertility after artificial insemination (AI). That activity was partially purified and termed universal primary sperm-egg binding protein (UPSEBP). Insufficient protein remained from 6 x 10(11) sperm, despite retention of bioactivity, to allow sequencing. We deduced that the protein may be related to prosaposin (also termed SGP-1, for sulfated glycoprotein-1), and we used published amino acid sequences of prosaposin as a guide for synthesis of peptides. Certain peptides were found to increase in vitro sperm-egg binding and increase fertility of frozen-thawed or fresh rooster sperm, in a manner similar to semipurified UPSEBP. Active epitopes were in a 60 amino acid sequence, reflecting the intervening sequence between saposins A and B, plus short extensions into saposins A and B. Highest activity was found when this synthetic peptide was oxidized to form a disulfide bond between terminal cysteines. Antibody against a synthetic peptide consisting of 58 of these 60 amino acids bound to a 7-9 kilodalton protein in UPSEBP. Collectively, the data support the conclusion that UPSEBP is a fragment of prosaposin. Because prosaposin is in semen in humans and animals, these observations have broad implications for possible cause and therapy of one type of subfertility.
Hammerstedt
R H
RH
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, USA. Hammer@biopore.com
Cramer
P G
PG
Barbato
G F
GF
Amann
R P
RP
O'Brien
J S
JS
Griswold
M D
MD
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D030161:Avian Proteins; D002352:Carrier Proteins / Q000302:isolation & purification / Q000494:pharmacology; D002645:Chickens / Q000502:physiology*; D002845:Chromatography; D005298:Fertility / Q000187:drug effects*; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification* / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology; D049231:Saposins; D013084:Sperm-Ovum Interactions / Q000187:drug effects*; D013094:Spermatozoa / Q000737:chemistry*; D049128:Sphingolipid Activator Proteins
D000906:Antibodies; D030161:Avian Proteins; D002352:Carrier Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D049231:Saposins; D049128:Sphingolipid Activator Proteins; C434548:UPSEBP protein, chicken