The effect of (o-phenanthroline) 2-cupric sulfate on several properties associated with (N-A+ + K+) -dependent adenosine triphosphatase
Archives of Biochemistry and Biophysics 180(2): 504-508
ISSN/ISBN: 0003-9861 PMID: 195525 DOI: 10.1016/0003-9861(77)90065-0
Previous studies have shown that the large polypeptide of purified NaK ATPase reacts to form a dimer and other higher oligomeric structures of the enzyme as a result of cross-linking with (o-phenanthroline)2-cupric sulfate (CP). The present study demonstrates that both NaK ATPase activity and p-nitrophenylphosphatase (NPPase) activity decline rapidly and nearly in parallel when the enzyme is reacted with CP. Similarly, ATP binding is lost with kinetics close to those of ATPase activity and NPPase activity. The loss of ATPase activity, NPPase activity and ATP binding occurs at a considerably faster rate than cross-linking of the large polypeptide, suggesting that CP may also be forming intrachain disulfide bonds. The binding of ouabain to NaK ATPase is also altered as a result of reacting the enzyme with CP. In marked contrast to ATP binding, ouabain binding is lost at a slower rate which closely parallels the rate of reaction of the large polypeptide to form cross-linked oligomeric structures.