J. Biol. Chem., Vol. 261, Issue 2, 663-668, 01, 1986
Purification and characterization of the major nucleoside triphosphatase from rat liver nuclear envelopes
HC Schroder, M Rottmann, M Bachmann and WE Muller
Nuclear envelopes contain a nucleoside triphosphatase. Hydrolysis of ATP or
GTP by this enzyme parallels energy-dependent efflux of poly(A)- containing
mRNA from nuclei in vitro. Nucleoside triphosphatase has been purified from
highly purified preparations of nuclear envelopes from rat liver by three
successive affinity steps. The essentially homogeneous enzyme has an
apparent molecular weight of 40,000 as checked by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and displays a rather broad
substrate specificity. ATP and GTP are hydrolyzed at nearly equal rates,
whereas UTP and CTP are only half as active as substrates. For optimal
activity, a one-to-one ratio of a divalent cation (Mg2+, Mn2+, or Ca2+) and
the nucleoside triphosphate substrate, an alkaline pH and a temperature of
34 degrees C are required. In contrast to the enzyme associated with
nuclear envelopes which is stimulated by synthetic poly(A) and the poly(A)
segment of the natural poly(A)-containing mRNA, homogeneous nucleoside
triphosphatase is unable to be modulated by this polynucleotide species.