The recombinant subdomain IIIB of human serum albumin displays activity of gonadotrophin surge-attenuating factor.
BACKGROUND
Gonadotrophin surge-attenuating factor (GnSAF) is an as yet unidentified ovarian factor that acts on the pituitary to attenuate the pre-ovulatory LH surge. In a previous study, GnSAF bioactivity was proposed to derive, at least in part, from a C-terminal domain (95peptide) of human serum albumin (HSA).


RESULTS
We employ here the expression-secretion system of Pichia pastoris to produce and assay selected recombinant polypeptides of HSA for GnSAF activity. We show that the C-terminal 95peptide of HSA (residues 490-585; subdomain IIIB) can be expressed from P.pastoris in secreted form and supernatants from clones expressing this polypeptide reduce the GnRH-induced LH secretion of primary rat pituitary cultures by 50-82%. When expressed in the same system, HSA domain III (residues 381-585) or full-length HSA (residues 1-585) are inactive. The bioactive subdomain IIIB is also separable from either domain III or full-length HSA on Blue Sepharose chromatography.


CONCLUSIONS
Taken together, the findings highlight the putative importance of HSA subdomain IIIB as a GnSAF-bioactive entity and introduce a unique experimental tool to engineer this molecule for structure-function analysis.
Tavoulari
Sotiria
S
Laboratory of Biological Chemistry, University of Ioannina Medical School, Ioannina 45110, USA.
Frillingos
Stathis
S
Karatza
Panayiota
P
Messinis
Ioannis E
IE
Seferiadis
Konstantin
K
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002478:Cells, Cultured; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D042341:Gonadal Hormones; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D010843:Pichia / Q000378:metabolism; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D012709:Serum Albumin / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D000075462:Serum Albumin, Human
D000906:Antibodies; D042341:Gonadal Hormones; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; D012709:Serum Albumin; C080538:attenuin; C026552:fragment C, human serum albumin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000075462:Serum Albumin, Human