Quaternary structure of (Na+ + K+)-dependent adenosine triphosphatase.
(Na+ + K+)-dependent adenosine triphosphatase (NaK-ATPase) consists of two polypeptide chains, a large polypeptide with a molecular weight of about 100,000, and a sialoglycoprotein with a molecular weight of about 40,000. Cross-linking of purified NaK-ATPase with the (o-phenanthroline)2-cupric ion complex (CP) results in the reversible formation of dimers, trimers, tetramers, and pentamers of the large polypeptide and loss of NaK-ATPase activity. ATPase activity is partially recovered if NaK-ATPase is incubated with beta-mercaptoethanol after treatment with CP. In contrast to these results, if NaK-ATPase is cross-linked in crude canine kidney microsomes, only a dimer of the large polypeptide is formed. No cross-linking of the sialoglycoprotein to the large polypeptide is detected when NaK-ATPase is cross-linked in purified form. However, when NaK-ATPase is reacted with CP in either purified or microsomal form, the sialoglycoprotein cross-links to itself yielding a high molecular weight aggregate. The results show that the functional subunit structure of NaK-ATPase consists of at least two large polypeptides.
D000818:Animals; D003300:Copper / Q000494:pharmacology; D004285:Dogs; D004789:Enzyme Activation / Q000187:drug effects; D006023:Glycoproteins / Q000032:analysis; D007668:Kidney / Q000201:enzymology; D046911:Macromolecular Substances; D008566:Membranes / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D008970:Molecular Weight; D010618:Phenanthrolines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011487:Protein Conformation; D012794:Sialic Acids / Q000032:analysis
D006023:Glycoproteins; D046911:Macromolecular Substances; D010618:Phenanthrolines; D012794:Sialic Acids; D003300:Copper; D011188:Potassium