Noguchi S, Higashi K, Kawamura M
Department of Biology and Biochemistry, University of Occupational and Environmental Health, Kitakyushu, Japan.
J Biol Chem. 1990 Sep 15;265(26):15991-5.
mRNAs from the alpha- and beta-subunits (mRNA alpha and mRNA beta, respectively) of Torpedo californica (Na,K)-ATPase were injected into Xenopus laevis oocytes either separately or in combination, and the properties of the two subunits synthesized were studied. The alpha-subunit synthesized in oocytes injected with mRNA alpha alone was recovered in both the membrane and cytosol fractions and was susceptible to tryptic attack. When mRNA beta was coinjected with mRNA alpha, almost all the alpha-subunit was found in the membrane fraction and was resistant to trypsin. In all cases, essentially all of the beta-subunit was recovered in the membrane fraction and was resistant to trypsin. As the amount of mRNA beta coinjected increased, the amounts of both the alpha- and beta-subunits as well as (Na,K)-ATPase activity of the membrane fraction increased. These results suggest that the beta-subunit facilitates the correct assembly of the alpha-subunit into the membrane probably by forming a stable complex with the nascent alpha-subunit.
分别或联合将加州电鳐（Na，K）-ATP酶的α亚基和β亚基的mRNA（分别为mRNAα和mRNAβ）注射到非洲爪蟾卵母细胞中，并研究合成的这两个亚基的特性。单独注射mRNAα的卵母细胞中合成的α亚基在膜和胞质溶胶组分中均有回收，且易受胰蛋白酶攻击。当mRNAβ与mRNAα共注射时，几乎所有的α亚基都存在于膜组分中，且对胰蛋白酶有抗性。在所有情况下，基本上所有的β亚基都在膜组分中回收，且对胰蛋白酶有抗性。随着共注射的mRNAβ量增加，α亚基和β亚基的量以及膜组分的（Na，K）-ATP酶活性均增加。这些结果表明，β亚基可能通过与新生的α亚基形成稳定的复合物来促进α亚基正确组装到膜中。
