Ouabain sensitivity of the alpha 3 isozyme of rat Na,K-ATPase.
The Na,K-ATPase of rat brainstem axolemma membranes contains two isozymes of its catalytic subunit, alpha 2 and alpha 3. To isolate the alpha 3 isozyme functionally, purified axolemma Na,K-ATPase was treated with trypsin. Immunoblot analysis of trypsin-treated Na,K-ATPase using isozyme-specific antibodies showed that alpha 3 was significantly more resistant to digestion than alpha 2. The trypsin-resistant alpha 3 isozyme fraction, devoid of alpha 2, contained 50-60% of the ATPase activity, and was inhibited by ouabain half-maximally at 0.13 microM. This indicates that the alpha 3 Na,K-ATPase isozyme has a high sensitivity to cardiac glycosides.
Urayama
O
O
Neurosurgical Research, Massachusetts General Hospital, Boston 02114.
Sweadner
K J
KJ
D000818:Animals; D000911:Antibodies, Monoclonal; D001369:Axons / Q000201:enzymology; D001933:Brain Stem / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008970:Molecular Weight; D010042:Ouabain / Q000494:pharmacology*; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D007527:Isoenzymes; D010446:Peptide Fragments; D010042:Ouabain; D014357:Trypsin; D000254:Sodium-Potassium-Exchanging ATPase