Affinity purification of mannose 6‐phosphate receptor proteins. Purification and partial characterisation of goat liver receptors

Abstract

Mannose 6-phosphate receptor (MPR) proteins designated as MPR 300 and MPR 46 have earlier been purified from some mammals on phosphomannan coupled to cyanogen bromide activated Sepharose. In a recent study, the goat liver MPR 300 has been directly purified using Sepharose-divinylsulfone-pentamannosyl phosphate matrix (Sivakumar N. 1996, J. Biochem. Biophys. methods, 31, 181-184(1)). In the present report, we describe the preparation of another affinity matrix Sepharose-divinylsulfone-phosphomannan and its utility in purifying the MPR proteins from goat liver. While the MPR 300 from goat liver showed an electrophoretic mobility similar to other mammalian MPRs, the small receptor showed a molecular weight of 36 kDa. Antibodies raised against goat liver MPR 300 react specifically with the large receptor protein. Additionally affinity purified peptide specific antibody corresponding to amino-acid residues 26-42 (ADGCDFVCRSKPRNVPA) of the cytoplasmic tail of the human liver MPR 46 (Pohlmann et al, 1988. Proc. Natl. Acad. Sci. USA, 84, 5575-5579 (2)) cross-reacts with the purified small receptor.