Open AccessSequence of a second human asialoglycoprotein receptor: conservation of two receptor genes during evolution.
Author(s) -
Martin Spiess,
Harvey F. Lodish
Publication year - 1985
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.82.19.6465
Subject(s) - asialoglycoprotein receptor , biology , complementary dna , microbiology and biotechnology , cdna library , rna , gene , receptor , homology (biology) , peptide sequence , messenger rna , biochemistry , in vitro , hepatocyte
The asialoglycoprotein (ASGP) receptor isolated from human liver and from the human hepatoma cell line HepG2 migrates on NaDodSO4 gel electrophoresis as a single species of 45,000 daltons. Recently, we isolated a cDNA clone encoding this receptor (H1) from a HepG2 lambda gt11 library. From the same library, we have isolated and sequenced a clone encoding a second ASGP receptor, H2, with a protein sequence homology of 58% to H1. There are two subspecies of H2 that differ only by the presence of a five-amino acid insertion in the COOH-terminal extracytoplasmic domain. Comparison with the available sequences of the two rat ASGP receptors R1 and R2 indicates that H1 is more homologous to R1 than to H2, and H2 is more similar to R2 than to H1. Thus, the two receptor genes evolved before the separation of rat and man. As judged by RNA blot hybridization of HepG2 RNA using RNA transcribed in vitro from cDNA clones of the human receptors as standards, H1 and H2 mRNA are present in equimolar amounts, each 0.005-0.01% of the total mRNA. This finding raises the question of whether the three ASGP receptor proteins are functional as heterodimers or whether they might serve different functions in the cell.