ROLE OF THE C-TERMINI OF HUMAN AND CHICKEN PLASMA RETINOL-BINDING-PROTEINS

The most prominent differences between mammalian and nonmammalian vert ebrate retinol-binding proteins (REP) are in the C-terminal sequences, We have cloned and sequenced the cDNA for chicken REP. Transfected CO S cells that transiently expressed mammalian (human) or non-mammalian (chicken) REP were used to demonstrate that both proteins were able to bind retinol and human transthyretin, However, we observed an increas ed retinol-independent secretion in cells expressing chicken REP and r educed ligand-dependent secretion compared to the human protein, It ca n therefore be concluded that the C-terminal amino acid tail which is missing in chicken REP compared to human REP might play a role in rete ntion and ligand-induced secretion.