CHARACTERIZATION OF THE MACROPHAGE-MIGRATION INHIBITORY FACTOR-BINDING SITE OF SARCOLECTIN AND ITS RELATIONSHIP TO HUMAN SERUM-ALBUMIN

The sialic acid-binding protein sarcolectin from human placenta specif ically interacts with the lymphokine macrophage migration inhibitory f actor, enabling its convenient purification and histochemical localiza tion. After cyanogen bromide-mediated cleavage of sarcolectin one poly peptide with an apparent molecular weight of approximately 15,000 exhi bited binding capacity to the labelled lymphokine, as revealed by liga nd blotting. The N-terminal sequence stretch of this peptide is identi cal to the respective sequence of human serum albumin, following the i nternal methionine residue in position 298. Cleavage at a methionine m oiety in position 446 can explain the size of the 15 KDa product of ch emical degradation. Close similarity of circular dichroism of sarcolec tin and human serum albumin added further evidence to their structural similarity, calling for further studies to rigorously define their re lationship. (C) 1994 Academic Press, Inc.