cDNA cloning and localization of a band 3-related protein from ileum.
A Cl(-)-HCO3- exchanger in the brush-border membrane mediates active Cl- absorption and regulates intracellular pH in rabbit ileum. The molecular identity of the ileal Cl(-)-HCO3- exchanger has not been established. The best-characterized plasma membrane Cl(-)-HCO3- exchanger is erythroid band 3. Structurally related proteins in nonerythroid tissues comprise an anion exchanger (AE) family. We used the polymerase chain reaction to amplify and clone a cDNA encoding an ileal band 3-related protein (B3RP) from rabbit ileal enterocytes. The composite sequence is 3,909 bp and is predicted to encode a protein of 136 kDa. The deduced amino acid sequence is 95% identical to murine renal AE2, indicating that ileal B3RP is rabbit AE2. Antisera generated against a cytoplasmic fragment of ileal B3RP recognized a 160- to 170-kDa polypeptide in the brush-border membrane, but not the basolateral membrane, of ileal crypt and villus enterocytes. This correlates with previous studies indicating that a Cl(-)-HCO3- exchange is present in brush-border but not basolateral membrane vesicles from rabbit ileal enterocytes. We conclude that ileal B3RP is a product of the AE gene family, and is present in the brush-border of ileal enterocytes, where it may mediate Cl(-)-HCO3- exchange.
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Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
Dobbins
J W
JW
Aronson
P S
PS
Igarashi
P
P
D000595:Amino Acid Sequence; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics*; D007082:Ileum / Q000166:cytology / Q000378:metabolism*; D015151:Immunoblotting; D008297:Male; D008969:Molecular Sequence Data; D011817:Rabbits; D014018:Tissue Distribution; D014158:Transcription, Genetic
D001457:Anion Exchange Protein 1, Erythrocyte; D004247:DNA