Detergent Solubilization of Membrane-Bound Methane Monooxygenase Requires Plastoquinol Analogs as Electron Donors

Arch Biochem Biophys. 1995 Aug 20;321(2):421-8. doi: 10.1006/abbi.1995.1413.

Abstract

Quinols can provide reducing equivalents for the membrane-bound form of methane monooxygenase (pMMO), substituting for NADH in whole cells and membranes. Furthermore, quinols are effective reductants for the detergent-solubilized enzyme, whereas NADH is ineffective. The decyl analog of plastoquinol and duroquinol (2,3,5,6-tetramethylbenzoquinol) provide the greatest methane monooxygenase activity in whole cells and membrane suspensions, as well as detergent-solubilized samples. Lauryl maltoside is by far the best detergent for solubilization of catalytically active methane monooxygenase. Optimal pMMO activity in the detergent-solubilized fraction is obtained with a ratio of approximately 1.7 mg of detergent per milligram of membrane protein, independent of protein concentration. The detergent-solubilized pMMO retains its sensitivity to inhibition by cyanide, acetylene, and EDTA. It is also stimulated by exogenous copper, as in isolated membrane fractions. Reaction of the detergent-solubilized enzyme with [14C]acetylene results in labeling of a 26-kDa peptide, analogous to the behavior observed for isolated membrane suspensions. The selectivity of pMMO for duroquinol and decyl-plastoquinol, relative to other structurally similar quinols, suggests that the enzyme obtains reducing equivalents directly from a quinol (probably plastoquinol) in vivo.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cell Membrane / enzymology
  • Detergents
  • Electron Transport
  • Euryarchaeota / enzymology*
  • Hydroquinones / pharmacology*
  • Kinetics
  • Oxygenases / isolation & purification*
  • Oxygenases / metabolism*
  • Plastoquinone / analogs & derivatives*
  • Plastoquinone / pharmacology
  • Solubility
  • Structure-Activity Relationship

Substances

  • Detergents
  • Hydroquinones
  • plastoquinol
  • Oxygenases
  • methane monooxygenase
  • Plastoquinone