TY - JOUR

T1 - Structure-function relationships of Na+, K+, ATP, or Mg2+ binding and energy transduction in Na,K-ATPase

AU - Jorgensen, Peter L.

AU - Pedersen, Per A.

PY - 2001/5/1

Y1 - 2001/5/1

N2 - The focus of this article is on progress in establishing structure-function relationships through site-directed mutagenesis and direct binding assay of Tl+, Rb+, K+, Na+, Mg2+ or free ATP at equilibrium in Na,K-ATPase. Direct binding may identify residues coordinating cations in the E2[2K] or E1P[3Na] forms of the ping-pong reaction sequence and allow estimates of their contributions to the change of Gibbs free energy of binding. This is required to understand the molecular basis for the pronounced Na/K selectivity at the cytoplasmic and extracellular surfaces. Intramembrane Glu327 in transmembrane segment M4, Glu779 in M5, Asp804 and Asp808 in M6 are essential for tight binding of K+ and Na+. Asn324 and Glu327 in M4, Thr774, Asn776, and Glu779 in 771-YTLTSNIPEITP of M5 contribute to Na+/K+ selectivity. Free ATP binding identifies Arg544 as essential for high affinity binding of ATP or ADP. In the 708-TGDGVND segment, mutations of Asp710 or Asn713 do not interfere with free ATP binding. Asp710 is essential and Asn713 is important for coordination of Mg2+ in the E1P[3Na] complex, but they do not contribute to Mg2+ binding in the E2P-ouabain complex. Transition to the E2P form involves a shift of Mg2+ coordination away from Asp710 and Asn713 and the two residues become more important for hydrolysis of the acyl phosphate bond at Asp369.

AB - The focus of this article is on progress in establishing structure-function relationships through site-directed mutagenesis and direct binding assay of Tl+, Rb+, K+, Na+, Mg2+ or free ATP at equilibrium in Na,K-ATPase. Direct binding may identify residues coordinating cations in the E2[2K] or E1P[3Na] forms of the ping-pong reaction sequence and allow estimates of their contributions to the change of Gibbs free energy of binding. This is required to understand the molecular basis for the pronounced Na/K selectivity at the cytoplasmic and extracellular surfaces. Intramembrane Glu327 in transmembrane segment M4, Glu779 in M5, Asp804 and Asp808 in M6 are essential for tight binding of K+ and Na+. Asn324 and Glu327 in M4, Thr774, Asn776, and Glu779 in 771-YTLTSNIPEITP of M5 contribute to Na+/K+ selectivity. Free ATP binding identifies Arg544 as essential for high affinity binding of ATP or ADP. In the 708-TGDGVND segment, mutations of Asp710 or Asn713 do not interfere with free ATP binding. Asp710 is essential and Asn713 is important for coordination of Mg2+ in the E1P[3Na] complex, but they do not contribute to Mg2+ binding in the E2P-ouabain complex. Transition to the E2P form involves a shift of Mg2+ coordination away from Asp710 and Asn713 and the two residues become more important for hydrolysis of the acyl phosphate bond at Asp369.

KW - ATP binding

KW - Cation binding site

KW - Energy transduction

KW - K binding

KW - Mg binding

KW - Mutagenesis

KW - Na,K-ATPase

KW - Na binding

KW - Tl binding

UR - http://www.scopus.com/inward/record.url?scp=0035342633&partnerID=8YFLogxK

U2 - 10.1016/S0005-2728(00)00277-2

DO - 10.1016/S0005-2728(00)00277-2

M3 - Review

C2 - 11248189

AN - SCOPUS:0035342633

VL - 1505

SP - 57

EP - 74

JO - B B A - Bioenergetics

JF - B B A - Bioenergetics

SN - 0005-2728

IS - 1

ER -