title: Beta 1- and beta 3-subunits can associate with presynthesized alpha-subunits of Xenopus oocyte Na,K-ATPase.
abstract: Oligomerization of newly synthesized alpha- and beta-subunits is a prerequisite for the structural and functional maturation of Na,K-ATPase. In this study, we have tested the competence of presynthesized alpha- and beta-subunits to assemble into functional enzyme complexes. Antisense oligonucleotides complementary to alpha-mRNA were used to inhibit alpha-subunit synthesis in Xenopus oocytes leaving a presynthesized trypsin-sensitive alpha-subunit pool. beta-Subunits expressed in these oocytes from injected cRNA assembled with the preexisting alpha-subunits, rendered them trypsin-resistant, and permitted the expression of more ouabain binding sites at the plasma membrane. Similarly, presynthesized beta 1- or beta 3-subunits produced in Xenopus oocytes by injection of beta-cRNA and later of specific antisense oligonucleotides were stabilized and transported out of the endoplasmic reticulum when alpha-cRNA was injected into oocytes. These data indicate that alpha- and beta-subunits can insert into endoplasmic reticulum membranes independent of each other in an assembly-competent form and retain their ability for oligomerization after synthesis.
authors.affiliation: Institut de Pharmacologie et de Toxicologie de l'Université, Lausanne, Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Ackermann
authors.forename: K
authors.initials: K
authors.lastname: Geering
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA; D006207:Half-Life; D008969:Molecular Sequence Data; D009865:Oocytes / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D011487:Protein Conformation; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism*; D014357:Trypsin; D014981:Xenopus
chemical_list: D010042:Ouabain; D004247:DNA; D014357:Trypsin; D000254:Sodium-Potassium-Exchanging ATPase