A NEW FAMILY OF HEPARIN-BINDING FACTORS - STRONG CONSERVATION OF MIDKINE (MK) SEQUENCES BETWEEN THE HUMAN AND THE MOUSE

A retinoic acid responsive gene, MK, specifies for a heparin binding factor termed midkine (MK), which is the initial member of a new protein family involved in regulation of growth and differentiation. A cDNA clone of human MK was isolated from a fetal kidney cDNA library. Human MK mRNA was expressed in PA1 teratocarcinoma cells as well as in the kidney. Sequence analysis of the cDNA clone and of a part of the genomic clone yielded the predicted protein sequence of human MK. Human and mouse MK sequences are highly conserved: 87% of amino acids are identical and all amino acid changes are conservative except for an insertion. Comparison of MK and HB-GAM / pleiotrophin (another member of the family) from various species revealed sequences conserved in the family and those specific for each protein. © 1991 Academic Press, Inc.