Cloning and functional characterization of a Na(+)-independent, broad-specific neutral amino acid transporter from mammalian intestine.
We have isolated a cDNA from a rabbit intestinal cDNA library which, when co-expressed with the heavy chain of the human 4F2 antigen (4F2hc) in mammalian cells, induces system L-like amino acid transport activity. This protein, called LAT2, consists of 535 amino acids and is distinct from LAT1 which also interacts with 4F2hc to induce system L-like amino acid transport activity. LAT2 does not interact with rBAT, a protein with a significant structural similarity to 4F2hc. The 4F2hc/LAT2-mediated transport process differs from the 4F2hc/LAT1-mediated transport in substrate specificity, substrate affinity, tissue distribution, interaction with D-amino acids, and pH-dependence. The 4F2hc/LAT2-associated transport process has a broad specificity towards neutral amino acids with K(t) values in the range of 100-1000 microM, does not interact with D-amino acids to any significant extent, and is stimulated by acidic pH. In contrast, the 4F2hc/LAT1-associated transport process has a narrower specificity towards neutral amino acids, but with comparatively higher affinity (K(t) values in the range of 10-20 microM), interacts with some D-amino acids with high affinity, and is not influenced by pH. LAT2 is expressed primarily in the small intestine and kidney, whereas LAT1 exhibits a much broader tissue distribution.
Rajan
D P
DP
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA.
Kekuda
R
R
Huang
W
W
Devoe
L D
LD
Leibach
F H
FH
Prasad
P D
PD
Ganapathy
V
V
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D026905:Amino Acid Transport Systems; D000596:Amino Acids; D002352:Carrier Proteins; D018076:DNA, Complementary; D005973:Glutamine