1. Isoform-specific interactions of Na,K-ATPase subunits are mediated via extracellular domains and carbohydrates
- Author
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Günther Schmalzing, Sergio M. Gloor, and Karina Ruhl
- Subjects
Gene isoform ,Models, Molecular ,Immunoprecipitation ,Protein Conformation ,Protein subunit ,Xenopus ,Plasma protein binding ,Mice ,Protein structure ,Enzyme Stability ,Animals ,Enzyme Inhibitors ,Ouabain ,G alpha subunit ,Glycoproteins ,Multidisciplinary ,biology ,Cell Polarity ,Biological Sciences ,biology.organism_classification ,Rats ,Isoenzymes ,Ectodomain ,Biochemistry ,Sodium-Potassium-Exchanging ATPase ,Protein Binding - Abstract
The functional unit of the Na,K-ATPase consists of a catalytic α subunit noncovalently linked with a glycoprotein subunit, β. Using ouabain binding assays and immunoprecipitation of rodent α/β complexes, we show here that all six possible isozymes between three α and two β isoforms can be formed inXenopusoocytes. Two isoform-specific differences in α/β interactions are observed: (i) α1/β1 and α2/β2 complexes, in contrast to α1/β2 complexes, are stable against Triton X-100-mediated dissociation, and (ii) β2 subunits must carryN-glycans to combine with α1 but not with α2. The interacting surfaces are mainly exposed to the extracellular side because coexpression of a truncated β1 subunit comprising the ectodomain results in assembly with α1 and α2, but not with α3; the β2 ectodomain combines with α2 only. A chimera consisting of 81% and 19% of the α1 N terminus and α2 C terminus, respectively, behaves like α2 and coprecipitates with the β2 ectodomain. In contrast, the reciprocal chimera does not coprecipitate with the β2 ectodomain. These results provide evidence for a selective interaction of Na,K-ATPase α and β subunits.
- Published
- 1997