Nucleotide occupancy of F1-ATPase catalytic sites under crystallization conditions

Sabine Löbau, Joachim Weber, Alan E. Senior

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Abstract

Using site-directed tryptophan fluorescence we studied nucleotide occupancy of the catalytic sites of Escherichia coli F1-ATPase, under conditions used previously for crystallization and X-ray structure analysis of the bovine mitochondrial enzyme [Abrahams et al. (1994) Nature 370, 621-628]. We found that only two of the three catalytic sites mere filled in the E. coli enzyme under these conditions (250 μM MgAMPPNP plus 5 μM MgADP), consistent with what was reported in the bovine F1 X-ray structure, However, subsequent addition of a physiological concentration of MgATP readily filled the third catalytic site. Therefore the enzyme form seen in the X-ray structure results from the fact that it is obtained under sub-saturating nucleotide conditions. The data show that the X-ray structure is compatible with a catalytic mechanism in which all three F1-ATPase catalytic sites must fill with MgATP to initiate steady-state hydrolysis [e,g, Weber and Senior (1996) Biochim. Biophys. Acta 1275, 101-104]. The data further demonstrate that the site-directed tryptophan fluorescence technique can provide valuable support for F1 crystallography studies.

Original languageEnglish
Pages (from-to)15-18
Number of pages4
JournalFEBS Letters
Volume404
Issue number1
DOIs
StatePublished - Mar 3 1997

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Keywords

  • Catalytic site
  • F-ATPase
  • Nucleotide occupancy
  • Oxidative phosphorylation

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