Primary structure of the β‐subunit of Torpedo californica (Na⁺ + K⁺)‐ATPase deduced from the cDNA sequence

Abstract

DNA complementary to the Torpedo cal~ornica electropiax mRNA coding for the ~-subunit of (Na+ + K +)-ATPase has been cloned by screening a cDNA library with an oligodeoxyribonucleotide probe. Nucleotide sequence analysis of the cloned cDNA has revealed that this polypeptide consists of 305 amino acid residues (including the initiating methionine). The transmembrane topology and the potential N-glycosylation sites of this polypeptide are discussed.

Advances in Na+,K+‐ATPase studies: from protein to gene and back to protein

“…Monospecific antibodies were successfully exploited to prove that the C-terminus of the a-subunit protrudes into the extracellular space [25,26]. However,some investigators suggest that the Cterminus has an intracellular location [ 14,151. The P-subunit sticks out into the lipid bilayer only once so that the major part of the polypeptide chain and the C-terminus are exposed outside the cell [17,18,27].…”

“…First, whether heterogeneity of the&subunits exists at the protein level, apart from the heterogeneity of glycosylation. &Subunit mRNAs from different sources (Torpedo [17], sheep, pig, dog and chicken [18,19,22,23], human HeLa cells [20], rat [21,83]) are cloned. In each case only the coding sequence was found.…”

Location of signal sequences for membrane insertion of the Na+,K+-ATPase alpha subunit.

“…Several studies have revealed that the ,B subunit does not have a cleavable signal peptide (11,20,26,27,29) and is inserted into rough microsomal membranes cotranslationally (11) in a signal recognition particle (SRP)-SRP receptormediated manner (9,18). A segment of 16 hydrophobic amino acids from the putative 28-residue transmembrane segment is a minimal requirement for the insertion of the ,B subunit (18).…”

Rat-brain Na,K-ATPase beta-chain gene: primary structure, tissue-specific expression, and amplification in ouabain-resistant HeLa C+ cells.

“…Comparison of the deduced amino acid sequence of rat brain p-subunit to the human (13) and Torpedo (17) proteins showed a striking degree of structural homology between the p-subunit polypeptides. The rat p-subunit gene encodes four mRNA species which are expressed in a tissue-specific fashion.…”