Identification of a candidate membrane protein for the basolateral peptide transporter of rat small intestine.
A candidate protein for the basolateral peptide transporter of rat jejunum is described. Vascular perfusion of the photoaffinity label, [4-azido-D-phe]-L-ala (2.5mM), had no effect on the transepithelial transport of the non-hydrolysable dipeptide D-phe-L-gln (1mM) from the lumen, its mucosal accumulation or wash-out into the vascular perfusate. When the label was perfused luminally, the transepithelial transport of D-phe-L-gln was inhibited by 38% (P<0.001) and accumulation increased by 62% (P<0.05). These data are consistent with those of a basolateral transporter that is strongly asymmetric in its substrate binding and transport properties. Labelling of basolateral membrane vesicles with [4-azido-3,5-3H-D-phe]-L-ala revealed that the majority of label was incorporated into a single protein of M(r)112+/-2 kDa and pI 6.5. MALDI-TOF analysis of tryptic digests of the protein followed by database searches established that this protein was novel with no obvious similarity to PepT1, the apical membrane transporter.
Shepherd
E J
EJ
Department of Biology, University of York, P.O. Box 373, York YO10 5YW, UK. ejs9@york.ac.uk
Lister
N
N
Affleck
J A
JA
Bronk
J R
JR
Kellett
G L
GL
Collier
I D
ID
Bailey
P D
PD
Boyd
C A R
CA
D000818:Animals; D001386:Azides / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D019992:Databases as Topic; D004847:Epithelial Cells / Q000378:metabolism*; D020224:Expressed Sequence Tags; D007583:Jejunum / Q000378:metabolism; D008027:Light; D008297:Male; D013058:Mass Spectrometry; D008956:Models, Chemical; D000074011:Peptide Transporter 1; D010477:Perfusion; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019920:Photoaffinity Labels / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D027981:Symporters; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
D001386:Azides; D002352:Carrier Proteins; D000074011:Peptide Transporter 1; D019920:Photoaffinity Labels; C489940:Slc15a1 protein, rat; D027981:Symporters; C027162:4-azidophenylalanine; D010649:Phenylalanine; D014357:Trypsin