MOLECULAR-CLONING OF A NOVEL ACTIN-BINDING PROTEIN, P57, WITH A WD REPEAT AND A LEUCINE-ZIPPER MOTIF

A 57 kDa protein (p57) was obtained during the study on phosphatidylin ositol-specific phospholipase C. Its cDNA was isolated from calf splee n and human leukemia cell line HL60 libraries and cloned, In the prima ry structures of p57, they have two unique amino acid sequence motifs, a WD repeat and a leucine zipper motif, Furthermore, p57 shared seque nce similarity (40%) with coronin, an actin-binding protein responsibl e for chemotaxis, cell motility, and cytokinesis of Dictyostelium disc oideum, which has only the WD repeat, p57 also showed an actin-binding activity and was mainly expressed in immune tissues, From these resul ts, we conclude that p57 is a coronin-like novel actin-binding protein in mammalian cells but may also have a different function from coroni n.