Inhibition of myosin ATPase by metal fluoride complexes

Sungjo Park, Katalin Ajtai, Thomas P Burghardt

Research output: Contribution to journalArticle

38 Citations (Scopus)

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

Fingerprint

Coordination Complexes
Myosins
Fluorides
Adenosine Diphosphate
Metals
Phosphates
Magnesium
Tryptophan
Catalytic Domain
Nucleotides
Myosin Subfragments
Gallium
Magnesium Chloride
Divalent Cations
Circular Dichroism
Edetic Acid
Adenosine Triphosphatases
Quenching
Adenosine Triphosphate
Fluorescence

Keywords

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

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Structural Biology
  • Biophysics

Cite this

Inhibition of myosin ATPase by metal fluoride complexes. / Park, Sungjo; Ajtai, Katalin; Burghardt, Thomas P.

In: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, Vol. 1430, No. 1, 10.02.1999, p. 127-140.

Research output: Contribution to journalArticle

Park, Sungjo ; Ajtai, Katalin ; Burghardt, Thomas P. / Inhibition of myosin ATPase by metal fluoride complexes. In: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology. 1999 ; Vol. 1430, No. 1. pp. 127-140.
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AB - 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.

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