Pflügers Archiv

, Volume 437, Issue 4, pp 517–522 | Cite as

Heterogeneity of Na+/K+-ATPase from rectal gland of Squalus acanthias is not due to α isoform diversity

  • O. Hansen


 Purified Na+/K+-ATPase (EC isolated from the rectal gland of Squalus acanthias was characterized in ouabain-binding studies and with respect to isoform(s) of the α peptide. To avoid enzyme inactivation [3H]ouabain equilibrium binding was carried out at 20°C. The heterogeneity of Na+/K+-ATPase isolated from shark rectal gland was similar in [3H]ouabain binding as previously seen in hydrolytic studies. The binding isotherms were compatible with the existence of a high-affinity (Kdis 0.69 nM) and a low-affinity (Kdis 42 nM) component of 1.46 and 0.79 nmol.(mg protein)–1, respectively. In Western blots the α peptide of the enzyme hybridized with an isoform-specific polyclonal antibody raised to an α3-specific region of the large intracellular domain of rat Na+/K+-ATPase, but not with the supposed α3-specific monoclonal antibody MA3-915 with its epitope near the N-terminus. Semi-quantitative analysis of the reaction of the α3-specific polyclonal antibody with the α peptide from the shark enzyme compared to the reaction with α peptide from rat brain enzyme indicated that this region is not exactly the same in the two species. The α peptide of shark enzyme was not recognized by α1- or α2-specific polyclonal antibodies, or by the α1-specific monoclonal antibodies 3B and F6. The large intracellular domain of Na+/K+-ATPase from shark rectal gland thus seems to be α3-like and no α isoform heterogeneity seems able to account for the heterogeneity seen in ouabain binding.

Key words Electronic autoradiography Enzyme heterogeneity α Isoforms Isoform-specific antibodies Na+/K+-ATPase [3H]Ouabain binding Shark rectal gland Squalus acanthias 


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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • O. Hansen
    • 1
  1. 1.Department of Physiology, Aarhus University, Ole Worms Allé 160, DK-8000 Århus C, Denmark e-mail: Tel.: +45-8942-2806; Fax: +45-8612-9065DK

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