Isolation and characterization of two isoforms of a retinoic acid-binding protein from rabbit epididymal secretions.
Two isoforms of a retinoic acid-binding protein have been purified from rabbit epididymal secretions using a combination of gel filtration and ion-exchange chromatography. The two polypeptides (EP21a and b) present similar molecular mass (21 kDa), under native or denaturing conditions and have very similar amino-acid composition and tryptic peptide maps but differ in net charge. Both isoforms are glycosilated though to a different extent (9.2% and 6.3% of carbohydrate content) and are major components of the epididymal fluid. Binding of retinoic acid to EP21s appears to be specific, since they do not bind retinol, but is non-saturable. EP21s seem to present some similarity to two retinoic acid-binding proteins from rat epididymal secretions (site of biosynthesis, androgen dependence, ligand specificity and association to the spermatozoa) but differ from the rat proteins in amino-acid composition and glycosilation.
Regalado
F
F
Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Spain.
Pérez Martínez
M
M
López de Haro
M S
MS
Nieto
A
A
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D001826:Body Fluids / Q000737:chemistry; D002241:Carbohydrates / Q000032:analysis; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004822:Epididymis / Q000378:metabolism*; D008297:Male; D008970:Molecular Weight; D011817:Rabbits; D018168:Receptors, Retinoic Acid / Q000737:chemistry / Q000302:isolation & purification*
D000596:Amino Acids; D002241:Carbohydrates; D018168:Receptors, Retinoic Acid