Hucolin, a new corticosteroid-binding protein from human plasma with structural similarities to ficolins, transforming growth factor-beta 1-binding proteins.

In order to study the cortisol-binding factors in blood, human plasma was applied to a 11 beta-hydroxy-3-oxo-4-androstene-17 beta-carboxyaminoethylamine-(HACA) 1,4-butanediol diglycidyl ether-Sepharose column. Elution of the column with cortisol buffer produced two protein peaks, the minor peak yielded a protein complex of molecular weight approximately 200 kDa, subsequently termed hucolin. SDS-PAGE analysis under reducing and non-reducing conditions revealed hucolin was a disulphide-linked complex of 35-kDa and 75-kDa subunits. Twenty-five amino acid residues of the N-terminus of the 35-kDa subunit were determined and homology searches revealed an 88% sequence identity with the N-terminal region of beta-ficolin, a transforming growth factor-beta 1 (TGF-beta 1)-binding protein purified from porcine uterus.