The effect of Pb(2+) ions on the Na(+),K(+)-ATPase was investigated in detail by means of steady-state fluorescence spectroscopy. Experiments were performed by using the electrochromic styryl dye RH421. It is shown that Pb(2+) ions can bind reversibly to the protein and do not affect the Na(+) and K(+) binding affinities in the E(1) and P-E(2) conformations of the enzyme. The pH titrations indicate that lead(II) favors binding of one H(+) to the P-E(2) conformation in the absence of K. A model scheme is proposed that accounts for the experimental results obtained for backdoor phosphorylation of the enzyme in the presence of Pb(2+) ions. Taken together, our results clearly indicate that Pb2+ bound to the enzyme stabilizes an E(2)-type conformation. In particular, under conditions that promote enzyme phosphorylation, Pb(2+) ions are able to confine the Na(+),K(+)-ATPase into a phosphorylated E(2) state.

Confining the sodium pump in a phosphoenzyme form: the effect of lead(II) ions / G. Bartolommei; E. Gramigni; F. Tadini-Buoninsegni; G. Santini; M.R. Moncelli. - In: BIOPHYSICAL JOURNAL. - ISSN 0006-3495. - STAMPA. - 99:(2010), pp. 2087-2096. [10.1016/j.bpj.2010.07.050]

Confining the sodium pump in a phosphoenzyme form: the effect of lead(II) ions

BARTOLOMMEI, GIANLUCA;GRAMIGNI, ELISA;TADINI BUONINSEGNI, FRANCESCO;SANTINI, GIACOMO;MONCELLI, MARIA ROSA
2010

Abstract

The effect of Pb(2+) ions on the Na(+),K(+)-ATPase was investigated in detail by means of steady-state fluorescence spectroscopy. Experiments were performed by using the electrochromic styryl dye RH421. It is shown that Pb(2+) ions can bind reversibly to the protein and do not affect the Na(+) and K(+) binding affinities in the E(1) and P-E(2) conformations of the enzyme. The pH titrations indicate that lead(II) favors binding of one H(+) to the P-E(2) conformation in the absence of K. A model scheme is proposed that accounts for the experimental results obtained for backdoor phosphorylation of the enzyme in the presence of Pb(2+) ions. Taken together, our results clearly indicate that Pb2+ bound to the enzyme stabilizes an E(2)-type conformation. In particular, under conditions that promote enzyme phosphorylation, Pb(2+) ions are able to confine the Na(+),K(+)-ATPase into a phosphorylated E(2) state.
2010
99
2087
2096
G. Bartolommei; E. Gramigni; F. Tadini-Buoninsegni; G. Santini; M.R. Moncelli
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/397394
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