HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Spector, M. Articles by Racker, E. Search for Related Content PubMed PubMed Citation Articles by Spector, M. Articles by Racker, E. Social Bookmarking                      What's this?

J. Biol. Chem., Vol. 255, Issue 18, 8370-8373, 09, 1980

Phosphorylation of the beta subunit of Na+K+-ATPase in Ehrlich ascites tumor by a membrane-bound protein kinase

M Spector, S O'Neal and E Racker

We have shown previously that proteoliposomes reconstituted with purified Na+K+-ATPase from Ehrlich ascites tumor cells, transport Na+ with low efficiency (Spector, M., O'Neal, S. and Racker, E. (1980) J. Biol. Chem., 255, 5504-5507). We now present evidence that this low efficiency (expressed in the ratio of Na+-transported/ATP-hydrolyzed) is caused by the phosphorylation of the beta subunit of the Na+K+- ATPase by an endogenous protein kinase. On addition of [gamma-32P]ATP, crude tumor plasma membrane preparations phosphorylated the beta subunit of the ATPase, whereas crude mouse brain plasma membranes did not. However, solubilized Na+K+-ATPase from either tumor or brain wre phosphorylated by purified protein kinase from the tumor plasma membrane and dephosphorylated by a phosphatase. In both cases, the phosphorylated enzyme was inefficient; the dephosphorylated enzyme was efficient after reconstitution into liposomes. During isolation of the Na+K+-ATPase from Ehrlich ascites tumor or mouse brain, an endogenous protease partially cleaved from the beta subunit a polypeptide of 29,000 daltons that contained the phosphorylation site. The proteolytic cleavage of the beta subunit was partially inhibited by phenylmethylsulfonyl fluoride and the major site of phosphorylation was then seen in the 53,000-dalton beta subunit of the enzyme. The isolated 29,000-dalton polypeptide from mouse brain ATPase was phosphorylated by tumor protein kinase with a stoichiometry of 1 mol of phosphate/mol of protein. When this 29,000-dalton polypeptide from mouse brain was incorporated into the tumor Na+K+-ATPase after mild proteolytic digestion, a marked increase in efficiency was observed after reconstitution of the Na+ pump.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				R. Ouwerkerk, K. B. Bleich, J. S. Gillen, M. G. Pomper, and P. A. Bottomley Tissue Sodium Concentration in Human Brain Tumors as Measured with 23Na MR Imaging Radiology, May 1, 2003; 227(2): 529 - 537. [Abstract] [Full Text] [PDF]

				E. Estrada, P. Agostinis, J. R. Vandenheede, J. Goris, W. Merlevede, J. Francois, A. Goffeau, and M. Ghislain Phosphorylation of Yeast Plasma Membrane H+-ATPase by Casein Kinase I J. Biol. Chem., December 13, 1996; 271(50): 32064 - 32072. [Abstract] [Full Text] [PDF]

				E Racker and M Spector Warburg effect revisited: merger of biochemistry and molecular biology Science, July 17, 1981; 213(4505): 303 - 307. [PDF]