Photoaffinity labeling of (Na+K+)-ATPase with [125I]iodoazidocymarin.

Lowndes, Joseph M.; Hokin-Neaverson, Mabel; Ruoho, Arnold E.

doi:10.1016/s0021-9258(18)90996-8

Cited by 18 publications

(2 citation statements)

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“…specialized cellular functions (for review, see Horisberger, On the other hand, photoaffinity-labeled ouabain deriv-1994). The Na,K-ATPase is composed of at least a catalytic atives can bind to the γ subunit (Forbush et al, 1978; α subunit of ™100 kDa and a smaller, glycosylated β Lowndes et al, 1984;Mercer et al, 1993), suggesting subunit. The α subunit is a large polytopic membrane that the γ subunit may be part of the ouabain-binding site.…”

Section: Introductionmentioning

confidence: 99%

“…Dissociation of the γ subunit from purified Na,K‐ATPase preparations with detergent did not result in loss of the ATPase activity (Hardwicke and Freytag, 1981), indicating that it is not essential for ATP hydrolysis. On the other hand, photoaffinity‐labeled ouabain derivatives can bind to the γ subunit (Forbush et al ., 1978; Lowndes et al ., 1984; Mercer et al ., 1993), suggesting that the γ subunit may be part of the ouabain‐binding site. However, co‐expression of the γ subunit with Na,K‐ATPase in yeast, devoid of endogenous γ subunits, did not reveal any modification in ouabain binding or inhibition of pump activity (Scheiner‐Bobis and Farley, 1994).…”

Section: Introductionmentioning

confidence: 99%

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The gamma subunit is a specific component of the Na,K-ATPase and modulates its transport function

1997

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The role of small, hydrophobic peptides that are associated with ion pumps or channels is still poorly understood. By using the Xenopus oocyte as an expression system, we have characterized the structural and functional properties of the γ peptide which co‐purifies with Na,K‐ATPase. Immuno‐radiolabeling of epitope‐tagged γ subunits in intact oocytes and protease protection assays show that the γ peptide is a type I membrane protein lacking a signal sequence and exposing the N‐terminus to the extracytoplasmic side. Co‐expression of the rat or Xenopus γ subunit with various proteins in the oocyte reveals that it specifically associates only with isozymes of Na,K‐ATPase. The γ peptide does not influence the formation and cell surface expression of functional Na,K‐ATPase α–β complexes. On the other hand, the γ peptide itself needs association with Na,K‐ATPase in order to be stably expressed in the oocyte and to be transported efficiently to the plasma membrane. γ subunits do not associate with individual α or β subunits but only interact with assembled, transport‐competent α–β complexes. Finally, electrophysiological measurements indicate that the γ peptide modulates the K+ activation of Na,K pumps. These data document for the first time the membrane topology, the specificity of association and a potential functional role for the γ subunit of Na,K‐ATPase.

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Section: Introductionmentioning

confidence: 99%