cDNA cloning of the human retinal rod Na-Ca + K exchanger: comparison with a revised bovine sequence

Invest Ophthalmol Vis Sci. 1998 Feb;39(2):435-40.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Buffaloes
  • Calcium / metabolism
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cattle
  • Cloning, Molecular
  • DNA Primers / chemistry
  • DNA, Complementary / analysis*
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism
  • Humans
  • Molecular Sequence Data
  • Potassium / metabolism
  • Rod Cell Outer Segment / metabolism
  • Sequence Homology, Amino Acid
  • Sodium / metabolism
  • Sodium-Calcium Exchanger*

Substances

  • Carrier Proteins
  • DNA Primers
  • DNA, Complementary
  • Eye Proteins
  • Sodium-Calcium Exchanger
  • potassium-dependent sodium-calcium exchanger
  • Sodium
  • Potassium
  • Calcium

Associated data

  • GENBANK/AF025480