The role of a membrane-associated folate binding protein (mFBP) in transport of folate analogues was investigated in three epithelial cell lines that were grown in high folate medium and folate-conditioned medium and express different levels of mFBP: human nasopharyngeal KB cells, monkey kidney MA104 cells, and IGROV-I ovarian carcinoma cells. Folate analogues were selected for which mFBP exhib...

The reduced folate carrier (RFC) and the proton-coupled folate transporter (PCFT) are ubiquitously expressed in normal and malignant mammalian tissues and in human solid tumor cell lines. This article addresses the extent to which PCFT contributes to transport of pemetrexed and to the activities of this and other antifolates relative to RFC at physiological pH. Either RFC or PCFT cDNA was stabl...

6 conserved aspartate residues (designated " D " in amino acid notation) in the molecule (see figure) are permissive to change, but the other 2 (D109 and D156) are critical for function with resulting marked impairment or total loss of function when mutated. Why aspartate? This amino acid is more highly conserved than others because of several attributes that include a short side chain, a high ...

The properties of the folate transport system in H35 hepatoma cells have been studied by measuring the transport of (+)-5-methyltetrahydrofolate. Using initial rates of uptake, it has been demonstrated that the uptake is saturable, carrier mediated, and shared by methotrexate. The accumulation of ( + )-5-methyltetrahydrofoÃ-ate is concentrative, demonstrating the presence of an active transport...