Evidence that the newly cloned low‐density‐lipoprotein receptor related protein (LRP) is the α2‐macroglobulin receptor

Abstract
The human placental receptor (α2MR) for α2‐macroglobulin‐proteinase complexes contains 3 polypeptides of approx. 500 kDa, 85 kDa, and 40 kDa. N‐terminal sequence analysis of the 500 kDa and 85 kDa polypeptides, analysis of a random selection of peptides covering 536 residues from these polypeptides, and analysis of a 1772 bp cDNA encoding part of the 500 kDa polypeptide provide evidence that the 500 kDa and 85 kDa chains are the α‐ and β‐subunits, respectively, of a recently cloned hepatic membrane protein, termed the low density lipoprotein receptor related protein (LRP) (Herz, J., Hamann, U., Rogne, S., Myklebost, O., Gausepohl, H. and Stanley, K.K. (1988) EMBO J. 7, 4119‐4127; Herz, J., Kowal, R.C., Goldstein, J.L. and Brown, M.S. (1990) EMBO J. 9, 1769‐1776). N‐terminal sequence analysis of the 40 kDa polypeptide shows that it is of distinct genetic origin. It is suggested that LRP is the functional receptor for α2‐macroglobulin‐proteinase complexes (α2MR) and in addition may have as yet unsettled functions in lipoprotein metabolism.