Cox, John V. and Lazarides, Elias (1988) Alternative primary structures in the transmembrane domain of the chicken erythroid anion transporter. Molecular and Cellular Biology, 8 (3). pp. 1327-1335. ISSN 0270-7306 http://resolver.caltech.edu/CaltechAUTHORS:COXmcb88
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Isolation and characterization of the chicken erythroid anion transporter (band 3) cDNA clone, pCHB3-1, revealed that the chicken erythroid band 3 polypeptide is 844 amino acids in length with a predicted mass of 109,000 daltons. This polypeptide is composed of a hydrophilic N-terminal cytoplasmic domain and a hydrophobic C-terminal transmembrane domain. The approximately 90 N-terminal amino acids of the human and murine erythroid band 3 polypeptides are absent in the predicted sequence of the chicken erythroid band 3 polypeptide. The absence of this very acidic N-terminal region is consistent with the lack of binding of glyceraldehyde-3-phosphate dehydrogenase to chicken erythroid band 3, as well as the relatively basic isoelectric point observed for this molecule. The remainder of the cytoplasmic domain shows little similarity to the cytoplasmic domain of the murine and human erythroid band 3, with the exception of the putative ankyrin-binding site, which is highly conserved. In contrast, the transmembrane domain of the chicken band 3 polypeptide is very similar to that of the murine erythroid and human nonerythroid band 3 polypeptides. The transmembrane domain contains 10 hydrophobic regions that could potentially traverse the membrane 12 to 14 times. In addition, a variant of chicken erythroid band 3, pCHB3-2, was cloned in which one of the hydrophobic regions of pCHB3-1 is lacking. The transcript complementary to pCHB3-2 accumulated in chicken erythroid cells in a similar manner as the transcript complementary to pCHB3-1 during embryonic development. This is the first example of a transporter protein or ion channel with alternative primary structures in its membrane-spanning segments.
|Additional Information:||Copyright © 1988 by the American Society for Microbiology. Received 13 October 1987/Accepted 1 December 1987. We gratefully thank Nancy Vogelaar for her assistance in plotting the hydrophobicity profiles. We also thank Jeffrey Stack, Nigel Burns, and Frank Sangiorgi for their comments on the manuscript. This work was supported by Public Health Service grants AG06078A and HL35801A from the National Institutes of Health and by grant DCB8215658 from the National Science Foundation. J.V. Cox was supported by a postdoctoral fellowship from the American Heart Association, Greater Los Angeles Affiliate.|
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