Mannose 6-phosphate receptors (MPR 300 and MPR 46) from a teleostean fish (trout)

Mannose B-phosphate receptors (MPRs) are known to occur in mammals, birds, reptiles and amphibians. Here we provide evidence for the presence of two M PRs in fish, the earliest vertebrates. Using phosphomannan-Sepharose affini ty chromatography, MPR 300 was purified from liver membrane extract of trou t. The purified trout liver MPR 300 showed similar electrophoretic mobility as the goat liver receptor and a pH optimum of 7.0 for binding Co phosphom annan. The presence of MPR 46 in fish was shown by metabolically labelling embryonic fish cells (Xiphophorus) and immunoprecipitation with an antibody against the cytoplasmic tail of human MPR 46 (anti-MSCl). This antibody ha d recently been shown to immunoprecipitate MPR 46 also from reptiles and am phibians. (C) 1999 Elsevier Science Inc. All rights reserved.