February 1998
Volume 39, Issue 2
Free
Articles  |   February 1998
cDNA cloning of the human retinal rod Na-Ca + K exchanger: comparison with a revised bovine sequence.
Author Affiliations
  • J E Tucker
    Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Canada.
  • R J Winkfein
    Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Canada.
  • C B Cooper
    Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Canada.
  • P P Schnetkamp
    Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Canada.
Investigative Ophthalmology & Visual Science February 1998, Vol.39, 435-440. doi:
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      J E Tucker, R J Winkfein, C B Cooper, P P Schnetkamp; cDNA cloning of the human retinal rod Na-Ca + K exchanger: comparison with a revised bovine sequence.. Invest. Ophthalmol. Vis. Sci. 1998;39(2):435-440.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: To clone the complementary DNA of the human retinal rod Na-Ca + K exchanger. METHODS: A human retinal cDNA library was screened initially with a radiolabeled probe representing the entire bovine rod Na-Ca + K exchanger cDNA and subsequently with probes from polymerase chain reaction fragments of the human retinal rod Na-Ca + K exchanger obtained after the initial screen. Twelve positive clones were used to obtain the entire coding sequence of the human retinal rod Na-Ca + K exchanger. RESULTS: The cDNA of the human retinal rod Na-Ca + K exchanger codes for a protein of 1081 amino acids, which shows 64.3% overall identity with the bovine retinal rod Na-Ca + K exchanger at the amino acid level. The two sets of putative transmembrane-spanning domains and their short connecting loops showed the highest degree of identity (94%-95%), whereas the extracellular loop at the N terminus showed a 59% identity. The large cytosolic loop that bisects the two sets of transmembrane-spanning domains contained two large deletions in the human exchanger; the first deletion contains 18 amino acids, whereas the second deletion involves a series of repeats that are dominated by acidic amino acid residues observed in the bovine, but not in the human, sequence. The authors observed that the bovine sequence contains a ninth repeat in addition to the eight repeats of the published sequence. CONCLUSIONS: The authors cloned the cDNA of the human retinal rod Na-Ca + K exchanger as a first step in examining the possibility that this gene could be the locus of disease-causing mutations.

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