EBP-37, a New Elastin-Binding Protein in Human Plasma: Structural Similarity to Ficolins, Transforming Growth Factor-β1-Binding Proteins

Abstract

In order to study the elastin-binding factors in blood, human plasma was applied to an alpha-elastin-Sepharose column. The column-binding fraction contained a 37-kDa protein, which was tentatively named EBP-37. Partial amino acid sequences of EBP-37 were determined. It had collagenous and non-collagenous domains. Homology searches of the sequences revealed that the protein is very similar but not identical to ficolins, transforming growth factor-beta 1 (TGF-beta 1)-binding proteins from porcine uterus membranes. Direct interaction of EBP-37 with elastin was confirmed by demonstrating the binding of the isolated EBP-37 to alpha-elastin on a nitrocellulose membrane using the EBP-37-specific antiserum. The existence of oligomers and multimers crosslinked by disulfide bonds was demonstrated by immunoblot analysis. Possible functions of EBP-37 are discussed.

Hucolin, a new corticosteroid‐binding protein from human plasma with structural similarities to ficolins, transforming growth factor‐β1‐binding proteins

“…Another candidate for the human ficolin gene product has recently been identified [13]. Harumiya et al [13] report the purification of EBP-37, a novel elastin-binding protein from human plasma and presented 45 residues of exclusively internal amino acid sequence that included collagen like domains.…”

“…Harumiya et al [13] report the purification of EBP-37, a novel elastin-binding protein from human plasma and presented 45 residues of exclusively internal amino acid sequence that included collagen like domains. This protein exhibited greater than 72% direct amino acid sequence identity with porcine ficolins.…”

“…EBP-37 also has a disulphide-linked multimeric Lower case denotes the predicted ficolin signal sequence and asterisks mark residues of hucolin that are not shared by ~-ficolin. The sequence from the spliced variant of human fl-galactosidase (Human S-gal) [14] illustrates an elastin binding site and is aligned with the predicted homologous region of the ficolins [13]. structure similar to both hucolin and the ficolins, with a similar subunit molecular weight of 37-kDa.…”

“…structure similar to both hucolin and the ficolins, with a similar subunit molecular weight of 37-kDa. Harumiya et al [13] suggest, by homology with elastin-binding proteins such as human fl-galactosidase, for which the elastin binding site sequence has been determined [14] (Table 1), that the ficolins have an N-terminal elastin-binding region and predict that the ficolin N-terminal elastin-binding domain will be conserved in EBP-37, however, no N-terminal sequence data for EBP-37 was presented. The N-terminal data presented here not only demonstrates the high degree of conservation of the N-terminus between hucolin and the ficolins but supports the contention that hucolin has an elastin-binding site at the N-terminus and that hucolin and EBP-37 are identical or closely related proteins (Table 1).…”

“…It has been suggested, for EBP-37, that its elastin-binding function may serve to localise it to the extracellular matrix of blood vessels and that its collagen-like domains may bind to the Clq receptor [13]. When the roles of these proteins are being considered the part played by a steroid-binding site should be included as this may be a common feature or function of the hucolin/EBP-37/ficolin group.…”