FOLATE BINDING-PROTEIN - MOLECULAR CHARACTERIZATION AND TRANSCRIPT DISTRIBUTION IN PIG-LIVER, KIDNEY AND JEJUNUM

Folate-binding protein (FBP) was identified and characterized in a pig liver cDNA library by screening with a 0.6 kb fragment from the cDNA of FBP from a human KB cell cancer line. The cDNA of pig liver FBP inc luded 1230 bp containing 759 bp in the open reading frame with 80% sim ilarity to the human placenta FBP. The deduced 253 amino acid sequence showed 67-73% similarity to previous sequences and contained 16 conse rved cysteine residues, 11 tryptophan potential folate-binding sites, three sites for N-linked glycosylation and 14 hydrophobic C-terminal r esidues. Northern analysis and reverse transcriptase PCR identified tr anscripts in pig liver and kidney, but not in jejunal mucosa. Although defining the molecular structure of pig liver FBP, these studies sugg est that this protein participates in the regulation of folate uptake by liver and kidney membranes but is not involved in folate absorption .