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2025-01-01
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03 Saúde e Bem-EstarColecciones
- IOC - Artigos de Periódicos [12836]
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THE γ SUBUNIT OF NA⁺, K⁺-ATPASE: ROLE ON ATPASE ACTIVITY AND REGULATORY PHOSPHORYLATION BY PKA
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In kidney, Na⁺, K⁺-ATPase is an oligomer (αβγ) with equimolar amounts of essential α and β subunits and one small hydrophobic FXYD protein (γ subunit). This report describes γ subunit as an activator of pig kidney outer medulla Na⁺, K⁺-ATPase in aqueous medium. The effects of γ subunit on Na⁺, K⁺-ATPase were dose-dependent and preincubation-dependent. Changes in αβ/γ stoichiometry did not alter Kₘ₁ for ATP, and slightly increased Kₘ₂, but Vₘₐₓ was increased at both catalytic and regulatory sites. Hydroxylamine treatment of enzyme phosphorylated by ATP (E-P), in the presence of additional γ subunit, revealed that 52% of the E-P accumulation was not via acyl-phosphate formation. The γ subunit was phosphorylated by endogenous kinases and by commercial catalytic subunit of protein kinase A (PKA). Additionally, we demonstrated that PKA phosphorylation of γ subunit increased its capacity to stimulate ATP hydrolysis. These results suggest that γ subunit can act as an intrinsic Na⁺, K⁺-ATPase regulator in kidney.
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