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Titolo:
COMPETITION BETWEEN LI-MEMBRANE AND ATP - AN NMR AND FLUORESCENCE STUDY( AND MG2+ FOR THE PHOSPHATE GROUPS IN THE HUMAN ERYTHROCYTE)
Autore:
DEFREITAS DM; AMARI L; SRINIVASAN C; RONG QF; RAMASAMY R; ABRAHA A; GERALDES CFGC; BOYD MK;
Indirizzi:
LOYOLA UNIV,DEPT CHEM,6525 N SHERIDAN RD CHICAGO IL 60626 UNIV COIMBRA,DEPT BIOCHEM P-3400 COIMBRA PORTUGAL UNIV COIMBRA,CTR NEUROSCI P-3400 COIMBRA PORTUGAL
Titolo Testata:
Biochemistry
fascicolo: 14, volume: 33, anno: 1994,
pagine: 4101 - 4110
SICI:
0006-2960(1994)33:14<4101:CBLAA->2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR-MAGNETIC-RESONANCE; P-31 NMR; PHOSPHATIDYLSERINE BILAYERS; PHOSPHOLIPID-BILAYERS; DIVALENT-CATIONS; AQUEOUS-SOLUTION; DEUTERIUM NMR; LITHIUM; TRIPHOSPHATE; SPECTROSCOPY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
D.M. Defreitas et al., "COMPETITION BETWEEN LI-MEMBRANE AND ATP - AN NMR AND FLUORESCENCE STUDY( AND MG2+ FOR THE PHOSPHATE GROUPS IN THE HUMAN ERYTHROCYTE)", Biochemistry, 33(14), 1994, pp. 4101-4110

Abstract

We investigated the mechanism of competition between Li+ and Mg2+ in Li+-loaded human red blood cells (RBCs) by making Li-7 and P-31 NMR and fluorescence measurements. We used Li-7 NMR relaxation times to probe Li+ binding to the human RBC membrane and ATP; an increase in Mg2+ concentration caused an increase in both Li-7 T1 and T2 values in packed Li+-loaded RBCs, in suspensions of Li+-loaded RBC ghosts, in suspensions of Li+-containing RBC membrane, and in aqueous solutions of ATP, indicating competition between Li+ and Mg2+ for binding sites in the membrane and ATP. We found that increasing concentrations of either Lior Mg2+ in the presence of human RBC membrane caused an increase in the P-31 NMR chemical shift anisotropy parameter, which describes the observed axially symmetric powder pattern, indicating metal ion bindingto the phosphate groups in the membrane. Competition between Li+ and Mg2+ for phosphate groups in ATP and in the RBC membrane was also observed by both fluorescence measurements and P-31 NMR spectroscopy at low temperature. The ratio of the stoichiometric binding constants of Mg2+ to Li+ to the RBC membrane was approximately 20; the ratio of the conditional binding constants in the presence of a free intracellular ATP concentration of 0.2 mM was approximately 4, indicating that Li+ competes for approximately 20% of the Mg2+-binding sites in the RBC membrane. Our results indicate that, regardless of the spectroscopic method used, Li+ competes with Mg2+ for phosphate groups in both ATP and the RBC membrane; the extent of metal ion competition for the phosphate head groups of the phospholipids in the RBC membrane is enhanced by the presence of ATP. Competition between Li+ and Mg2+ for anionic phospholipids or Mg2+-activated proteins present in cell membranes may constitute the basis of a general molecular mechanism for Li+ action in human tissues.

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Documento generato il 24/11/20 alle ore 14:24:19