β Subunit Affects Na and K Affinities of Na/K-ATPase: Na and K Affinities of a Hybrid Na/K-ATPase Composed of Insect α and Mammalian β Subunits

Overview

Journal Biochem Biophys Rep

Specialty Biochemistry

Date 2022 Sep 22

PMID 36131851

Authors

Haruo Homareda

Kei Suga

Sachiko Yamamoto-Hijikata

Yoshinobu Eishi

Makoto Ushimaru

Yukichi Hara

Affiliations

Soon will be listed here.

Abstract

The affinity for K of silkworm Na/K-ATPase, which is composed of α and β subunits, is remarkably lower than that of mammalian Na/K-ATPase, with a slightly higher affinity for Na. Because the α subunit had more than 70% identity to the mammalian α subunit in the amino acid sequence, whereas the β subunit, a glycosylated protein, had less than 30% identity to the mammalian β subunit, it was suggested that the β subunit was involved in the affinities for Na and K of Na/K-ATPase. To confirm this hypothesis, we examined whether replacing the silkworm β subunit with the mammalian β subunit affected the affinities for Na and K of Na/K-ATPase. Cloned silkworm α and cloned rat β1 were co-expressed in BM-N cells, a cultured silkworm ovary-derived cell lacking endogenous Na/K-ATPase, to construct a hybrid Na/K-ATPase, in which the silkworm β subunit was replaced with the rat β1 subunit. The hybrid Na/K-ATPase increased the affinity for K by 4.1-fold and for Na by 0.65-fold compared to the wild-type one. Deglycosylation of the silkworm β subunit did not affect the K affinity. These results support the involvement of the β subunit in the Na and K affinities of Na/K-ATPase.

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