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Size of the plasma membrane H+-ATPase from Neurospora crassa determined by radiation inactivation and comparison with the sarcoplasmic reticulum Ca2+-ATPase from skeletal muscle - PubMed

  • ️Tue Jan 01 1985

Comparative Study

. 1985 Jul 25;260(15):8726-30.

  • PMID: 2862141

Free article

Comparative Study

Size of the plasma membrane H+-ATPase from Neurospora crassa determined by radiation inactivation and comparison with the sarcoplasmic reticulum Ca2+-ATPase from skeletal muscle

B J Bowman et al. J Biol Chem. 1985.

Free article

Abstract

Using radiation inactivation, we have measured the size of the H+-ATPase in Neurospora crassa plasma membranes. Membranes were exposed to either high energy electrons from a Van de Graaff generator or to gamma irradiation from 60Co. Both forms of radiation caused an exponential loss of ATPase activity in parallel with the physical destruction of the Mr = 104,000 polypeptide of which this enzyme is composed. By applying target theory, the size of the H+-ATPase in situ was found to be approximately 2.3 X 10(5) daltons. We also used radiation inactivation to measure the size of the Ca2+-ATPase of sarcoplasmic reticulum and got a value of approximately 2.4 X 10(5) daltons, in agreement with previous reports. By irradiating a mixture of Neurospora plasma membranes and rabbit sarcoplasmic reticulum, we directly compared the sizes of these two ATPases and found them to be essentially the same. We conclude that both H+-ATPase and Ca2+-ATPase are oligomeric enzymes, most likely composed of two approximately 100,000-dalton polypeptides.

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