Inhibition of myosin ATPase by metal fluoride complexes

Sungjo Park, Katalin Ajtai, Thomas P. Burghardt

Research output: Contribution to journalArticle

38 Scopus citations

Abstract

Magnesium (Mg2+) is the physiological divalent cation stabilizing nucleotide or nucleotide analog in the active site of myosin subfragment 1 (S1). In the presence of fluoride, Mg2+ and MgADP form a complex that traps the active site of S1 and inhibits myosin ATPase. The ATPase inactivation rate of the magnesium trapped S1 is comparable but smaller than the other known γ-phosphate analogs at 1.2 M-1 s-1 with 1 mM MgCl2. The observed molar ratio of Mg/S1 in this complex of 1.58 suggests that magnesium occupies the γ-phosphate position in the ATP binding site of S1 (S1-MgADP-MgF(x)). The stability of S1-MgADP-MgF(x) at 4°C was studied by EDTA chase experiments but decomposition was not observed. However, removal of excess fluoride causes full recovery of the K+-EDTA ATPase activity indicating that free fluoride is necessary for maintaining a stable trap and suggesting that the magnesium fluoride complex is bonded to the bridging oxygen of β-phosphate more loosely than the other known phosphate analogs. The structure of S1 in S1-MgADP-MgF(x) was studied with near ultraviolet circular dichroism, total tryptophan fluorescence, and tryptophan residue 510 quenching measurements. These data suggest that S1-MgADP-MgF(x) resembles the M**.ADP.P(i) steady-state intermediate of myosin ATPase. Gallium fluoride was found to compete with MgF(x) for the γ-phosphate site in S1-MgADP-MgF(x). The ionic radius and coordination geometry of magnesium, gallium and other known γ-phosphate analogs were compared and identified as important in determining which myosin ATPase intermediate the analog mimics. Copyright (C) 1999 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)127-140
Number of pages14
JournalBiochimica et Biophysica Acta - Protein Structure and Molecular Enzymology
Volume1430
Issue number1
DOIs
StatePublished - Feb 10 1999

Keywords

  • ATPase
  • Energy transduction
  • Gallium
  • Magnesium
  • Myosin tryptophan 510
  • Nucleotide analog
  • Probe binding cleft

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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