Differential influence of the 4F2 heavy chain and the protein related to b(0,+) amino acid transport on substrate affinity of the heteromeric b(0,+) amino acid transporter.
We provide evidence here that b(0,+) amino acid transporter (b(0, +)AT) interacts with 4F2 heavy chain (4F2hc) as well as with the protein related to b(0,+) amino acid transporter (rBAT) to constitute functionally competent b(0,+)-like amino acid transport systems. This evidence has been obtained by co-expression of b(0, +)AT and 4F2hc or b(0,+)AT and rBAT in human retinal pigment epithelial cells and in COS-1 cells. The ability to interact with 4F2hc and rBAT is demonstrable with mouse b(0,+)AT as well as with human b(0,+)AT. Even though both the 4F2hc x b(0,+)AT complex and the rBAT x b(0,+)AT complex exhibit substrate specificity that is characteristic of system b(0,+), these two complexes differ significantly in substrate affinity. The 4F2hc x b(0,+)AT complex has higher substrate affinity than the rBAT x b(0,+)AT complex. In situ hybridization studies demonstrate that the regional distribution pattern of mRNA in the kidney is identical for b(0,+)AT and 4F2hc. The pattern of rBAT mRNA expression is different from that of b(0,+)AT mRNA and 4F2hc mRNA, but there are regions in the kidney where b(0,+)AT mRNA expression overlaps with rBAT mRNA expression as well as with 4F2hc mRNA expression.
Rajan
D P
DP
Department of Biochemistry, Medical College of Georgia, Augusta, Georgia 30912, USA.
Huang
W
W
Kekuda
R
R
George
R L
RL
Wang
J
J
Conway
S J
SJ
Devoe
L D
LD
Leibach
F H
FH
Prasad
P D
PD
Ganapathy
V
V
D026905:Amino Acid Transport Systems; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D018076:DNA, Complementary; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
D026905:Amino Acid Transport Systems; D000596:Amino Acids; D002352:Carrier Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger