SUBSTITUTION OF ALANINE FOR SERINE-250 IN THE MURINE FATTY-ACID TRANSPORT PROTEIN INHIBITS LONG-CHAIN FATTY-ACID TRANSPORT

The murine fatty acid transport protein (FATP) was identified on the b asis of its ability to facilitate uptake of long chain fatty acids (LC FAs) when expressed in mammalian cells. To delineate FATP domains impo rtant for transport function, we cloned the human heart FATP ortholog, Comparison of the human, murine, and yeast amino acid sequences ident ified a highly conserved motif, IYTSGTTGXPK, also found in a number of proteins that form adenylated intermediates. We demonstrate that depl etion of intracellular ATP dramatically reduces FATP-mediated LCFA upt ake. Furthermore, wildtype FATP specifically binds [alpha-P-32]azido-A TP. Introduction of a serine to alanine substitution (S250A) in the IY TSGTTGXPK motif produces an appropriately expressed and metabolized mu tant FATP that demonstrates diminished LCFA transport function and dec reased [alpha-P-32]azido-ATP binding. These results are consistent wit h a mechanism of action for FATP involving ATP binding that is depende nt on serine 250 of the IYTSGTTGXPK motif.